I want to buy some cookies.
1. - How much is it?
2. - How much are they?
3. - It's two dollars.
4. - They are two dollars.
(In this short dialogue, which expressions do we have to use?)
cookies = plural
1. How much are they?
3. They are two dollars.
Use #2 and #4.
Sra
In this short dialogue, you can use either "How much is it?" or "How much are they?" to ask about the price of the cookies. Both expressions are correct and commonly used in this context.
For the response, you can either say "It's two dollars" or "They are two dollars" to inform about the price. Both expressions are acceptable, and the choice between them depends on how you prefer to refer to the cookies - as a singular item ("it") or a plural item ("they").