why is "it can be true" not correct?

English as a Second Language English Vocabulary, Grammar and Idioms
1

—Do you believe what he says?
—Yes，it __________ be true.
A. can B. could
why is “A” not correct

2

‘could’ indicates possibility/probability, which is required in this context.

3

How about “can”?"Can’ indicates possibility/probability as well.

4

Not as much as ‘could’ does. ‘Can’ indicates ‘ability’, rather than ‘possibility’
‘It could be true’ - emphasises the opinion that it is possible, but not certain.
‘It can be true’ - emphasizes simply the general statement that it is possible… It is not right in this context.

5

In the sentence"Peter can come with us tonight, but he isn’t very sure yet.", should we use "could’ instead of “can”?

6

In the sentence"Peter can come with us tonight, but he isn’t very sure yet.", should we use "could’ instead of “can”?

7

That sentence requires ‘might be able to’.
Peter might be able to come with us tonight, but he isn’t sure yet.

  • It is a possibility, but he is not yet certain.

In this context, you would use ‘could’ or ‘can’ if there was a condition involved:
Peter could come with us tonight if we ask him in time. - it is possible that he will come if we ask him in time.
Peter can come with us tonight if we ask him in time. - it is definite he will come if we ask him in time.