—Do you think I should go to the seaside for a rest?

—____________ You have been busy for such a long time.

A．It depends.

B．It’s up to you.

C． Why not?

D．What about you?

受体拮抗剂的特点为

A．对受体无亲和力，有内在活性
B．对受体有亲和力，有内在活性
C．对受体无亲和力，无内在活性
D．对受体有亲和力，无内在活性
E．使受体数目减少