I have the “problem” with singular and plural nouns. As you know, even my friend doesn’t have any childre. I have to say “He has no children” and not “He has no child.”
1/If I know my composition has only one mistake but I can’t find it. So, I give the teacher my composition. On this composition, can I write: Please fix the mistake?
Or I have to write: Please fix the mistakes?
2/I have 20 answers. I know only one of them is correct but I can’t find it. So, I put these answers in an envelop and give them to my teacher. On the envelop, can I write:
a. Please find the correct answer.
b. What answer is correct?
e. What is correct?
Or I have to write:
a. Please find the correct answers.
b. What answers are correct?
e. What are correct?
Always the problem with singular and plural. Please help me.
correct (means that he doesn’t have children at all)
(if you have only one mistake and you’re sure of it)
is Ok( if there is really only one correct answer and you’re sure of it)
is also Ok and I think that you implies by this answer that you’re sure that there is only one correct answer but you have no idea what answer exactly
“What is correct?” is also OK?
If I don’t know exactly how many mistakes there are in my composition as well as correct answers out of my answers,
I have to use the plural form. Ok?
How about what are correct?
What answers are correct.( when you want to find out what the correct answers are)
No,you don’tunderstand what I mean.
My idea is: The sentence
What answers are correct?
is correct in grammar and in meaning.
So,is the sentence:
What are correct?
correct in grammar and in meaning?
In colloq. speech I observed that but I don’t like it. It’s not correct in my way of thinking.
You may also say:
Which(of the) answers are correct?
Regarding the second question from your original post:
The questions about the “correct answer(s)” could (and probably should) have been written with which instead of what because there has been a specifically limited / given group of possibilities to choose from since the very beginning.
When the choices are spcifically limited or defined in advance, that’s a classic situation for the use of which in a question. It doesn’t matter whether the possible answers are “hidden” in an envelope or are clearly visible on a single piece of paper. The possible answers were limited to a specific, given group before the question was asked! Using what to ask the questions isn’t wrong in your theoretical situation, but which is technically better.
Regarding your question about “What are correct?”:
In my opinion, this sentence would always be grammatically wrong.
However, it’s perfectly OK to say “Which are correct?”
“What answers are correct?” is OK. But, for your example, “Which answers are correct?” is just as good, if not better (for the reason mentioned above). But this also assumes that more than one may be correct.
If you know in advance that only one of a given group of answers is correct, then you should say “Which (one) is correct?”