Identify the correct sentence.

A.

I had a very bad day.

B.

That is very true.

C.

I made a more eternal vow never to cheat again.

D.

We had very perfect weather on our wedding day.

C and D are definitely not correct.

C should not have the word more in it - I made an eternal vow ...

D should also omit the word very - We had perfect weather ...

Now, both A and B are technically correct. B is more colloquial, and the word very isn't that necessary there, so I'd go with A. But both of these sentences are definitely grammatically correct.