A2 used when you are giving or asking for information that is completely correct精确地；确切地；完全准确地
B1 used to emphasize what you are saying（用于强调）正好，恰好；究竟
used for saying that someone or something is slightly different from a particular way of describing him, her, or it算不上…，并非十分…
B2 used for saying that something is not completely true并不完全是这样
used for saying that something is the opposite of a particular way of describing it并非…
Please describe to the court exactly what you saw.
No one knows exactly what happened but several people have been hurt.
I don't know exactly what's wrong with her - I think it's some sort of virus.
This jug holds exactly one pint.
I wanted to tell him exactly what I thought of him, but I managed to stop myself.