—I was told to be here before 5:00 p.m.

—Oh, you __      __. I'm sorry for _      __ you that we've changed the plan. [ ]

A. can't; not tell

B. needn't; not telling

C. can't; not to tell

D. needn't; not tell

剪力的符号规定是：剪力使研究对象（）为正。