You are 83 months old and a quarter of the way through 1st grade.
That last test is timed and boy do you hate to be timed! I can't say I blame you--you and I are a lot alike in that respect. I tend to freeze up when asked a question under duress (and being timed is very much "under duress"!) and I can see the same thing happen to you when you are pressured to perform. I know that you know the answer but, like me, your brain just cannot access it when it is under pressure. Combine that with your vast reluctance to be wrong or to appear "stupid", and you clam up or just say you don't know.