--Hi,Mary.Would you like to go to the concert this evening?
----Hi,Mary.Would you like to go to the concert this evening?
----Sorry,Tom._____ tomorrow's lessons,I have no time to go out with you.
A,Not preparing.B,Not having prepared.C ,Not to prepare.D,Being not prepared.我感觉是C,可我们老师说是B,请网上大大们解惑,