In Old Common, there was no grammaticalised way to ask questions. Yes/no questions were distinguished by intonation alone, as in Spanish. For questions that would in English use a WH question word, Common used the indeterminate article 'ko' in whatever position of the sentence the element would normally occupy for an indicative statement, often with some object to clarify the intent. Since the early period, however, there has been significant development in the grammaticalisation of questions in Common.

One thing to note is that Peter Davidson never defined what was meant by 'intonation' signaling questions, and it seems that both he and the actors on the Hillbillies screenshow took it for granted that this would be identical to English. Due to the tremendous influence of English on Common, the intonation profile for High Common is in fact very close to English, and this kind of rising intonation at the end of the sentence is a pretty reliable signal of a question

Intonation

In speech, the main way of signaling a question is just intonation. There are clues the speaker can provide, like words that often function as question words, or a yes/no tag, but there is no mandatory, grammatical question marking in Common.

In Writing

In Common writing, questions are bracketed between an inverted question mark and a regular question mark, like ¿this? as in Spanish. In Common, it may be acceptable to put only a part of a sentence or a single word between question marks if that's the focus of the rising intonation.

Early Common was written without the leading inverted question marks, just as in the nation influence on Common punctuation, American English. But where Common depends more heavily than English on intonation to mark questions, people writing speeches to be read out loud found that placing a mark for the start of the part that should get Austin intonation helped the orator sound more natural, and people started borrowing the Spanish style of punctuation for that purpose. Early in the modern period, the AXZ made it the official correct style.

Tag Questions

The adverbial modifiers 'ikky' ('no') and 'la' ('yes') can be added as tags to the end of a sentence which, in combination with tone, can be used to mark a sentence as a question. In this case, the particle is not usually echoed inside  the verb phrase, although it can be. See the lexeme entries for 'la' and 'ikky' for more information about the phenomenon of echoing. Essentially, in the normal usage of these particles to indicate the polarity of the verb, they must appear right before the verbal terms, but may be echoed in a different part of the sentence. Use as tag question particles, however, voids this requirement. Examples of tag questions:

¿A costo se an uzre, ikky?
The house is green, no?

¿A costo se an uzre, la?
The house is green, yes?

When responding to such a question, the same particles can be used to introduce the answer, but they must be echoed by another polarity particle before the verbal terms as well. Examples of responding 'no' in both a negative and a positive sense:

Ikky, a costo se ikky an uzre.
No, the house is not green.

Ikky, a costo se la an uzre.
No, the house is green.

'Ko' Questions

'Ko' questions in Common are the equivalent of WH-word questions in English. 'Ko' is an article, specifically an indeterminate article, which inflects for case and number just like a regular third person article, but not for definiteness. It translates approximately as 'what'. In order to make proper question words, 'ko' is used with a head term that clarifies the type of thing being asked - although this head term can be omitted. In its nominative forms, 'ko' can also be the object of a preposition in question expressions.

The question phrases constructed this way may be fronted but it is but a requirement or even a strong tendency. Generally they appear wherever the equivalent element would appear in a declarative sentence.

Not every sentence where an element is introduced with 'ko' is a question. 'Ko' can also have a sense like 'which', or 'whichever'. Example:

Co pikki su si ates ruil te slek a skitrem.
what(ERG) cat that(ABS) stand(NP.IM.IR) one-ORD wake hit(NP.IM) eat the(ABS) mouse.

Whichever cat wakes up first will eat the mouse.

In this sentence, 'co' is the singular ergative form of 'ko'.

Basically, when used in a question, 'ko' signals the questionable element that the speaker would like to have more information about. It declines for case and number as follows:

The interrogative/uncertain article 'ko' inflects for number in Common, which can be a little unfamiliar for speakers of languages that don't have this concept on these types of words, like English. Some of these uses are idiomatic and just have to be learnt. As a general rule, the number of the article should match the number you expect in the response. The paucal should be chosen when you want a number of discrete things explicitly listed, and the plural when you're talking about a bunch of things and don't expect individuals to be picked out. The paucal can also be used if you want an exact number as the response.

Here is a listing of expressions in Common that are equivalent to WH- words in English: Note that there isn't an exact one-to-one, and what is provided are possible, suggested translations of common English question words. In Common, there may be different forms depending on whether the expression functions adverbially or whether it is a thematic argument to a verb.

Words for 'how' create some of the worst problems for English-speaking learners. There are two expressions that typically translate as 'how', 'lo kon' and 'kon kaje'. The former is used to inquire as to condition of a person or thing, manner of an action, or a fact. The latter is used when the speaker wants step-by-step directions to accomplish something or is inquiring about the means by which something was done.

For example, given the expression:

¿Lo kon a sy sea falu?
How did the person arrive?

Some possible answers are:

Usútta na cejákki.
With their older brother.

Esif.
Quickly.

Cajre.
On time.

But if the question is phrased:

¿Kon kaje a sy sea falu?
How did the person arrive?

None of the above answers are appropriate. An appropriate response might be:

Ceo ny zom.
By car.

E na hajwe.
On the highway.

Quantities and Time Spans

Asking 'how much' or 'how many' is done with 'ko' using paucal forms. Although 'how much' and 'how many' are really two different questions - you can say 'how many apples' and it makes sense. but unless you're talking about something like glases of water, 'how many waters' doesn't make sense, you would ask 'how much water' and expect a response in some kind of unit. Common, however, treats them as the same. Effectively, Common treats continuous substances as though they were inherently subdivided.

There are two basic idioms that are essentially interchangeable:

1. Direct paucal forms of 'ko' with the thing being counted as its object.
2. The expression 'ko tret', 'what number', with the thing counted introduced with the null preposition - this reads like 'what number of X'

The latter form is actually older. The former started to be seen once Common had native speakers and was first seen in the generation that grew up speaking Common. It takes advantage of the fact that in Common, the paucal is used for exact quantities. Idiomatically, these forms came to be interpreted as actually asking about the quantity rather than the identity of the referent.

That said, the 'kor' forms can sometimes be interpreted as a request to enumerate rather than provide a quantity - the 'ko tret' forms are more unambigiously clear that a number is requested.

Examples:

¿Ju te sif kor pikki?
2.SG.ERG hit(NP.IM) hold Q.PA.ABS cat?
How many cats do you have?

¿Ju te sif ko tret nyr pikki?
2.SG.ERG hit(NP.IM) hold Q.SG.ABS count ∅ 3.PA.NDEF.NOM cat?
How many cats do you have?

The answer might be:

Je te sif yr net yn.
1.SG.ERG hit(NP.IM) hold 3.PA.NDEF.ABS three TER.
I have three cats.

Notice also in this exchange, the indefinite form is used in response, and also in the second case, in the question. When the 'ko tret' form is used, the definiteness of the thing counted typically depends on whether it was mentioned before in the discourse or whether this is the point where the referent is being introduced. In the latter case the indefinite will be used, and in the former case, where the topic was already introduced, the definite would be used.

In the response, the indefinite is usually always used. The only time the definite would be used would be when  the object in question was previously mentioned, and you are counting all of it in existence (which might be reinforced with 'awke').

Asking 'how long' as in time is handled with this sort of idiom with 'cel' as the thing counted, where the event  being inquired about can be introduced with 'u' or 'u sin' (usámor can be used instead of u). For this usage, 'ko tret na cel' sounds archaic and quaint, most people would always say 'kor cet'. Example:

¿Kor cel se an u sin wez nox falu?
Q.PA.ABS hour stand(NP.IM) be to RELV.NOM 1.PL.ABS go(NP.IM) arrive?
How long until we arrive?

Wez nox falu rokíle nyr akin cel.
1.PL.ABS go(NP.IM) arrive after 3.PA.NDEF.NOM four hour.
We'll arrive in four hours.