题目

---Could you give me an explanation ______ your keeping silent throughout the discussion?     ---Oh, terribly sorry. I had the least idea of what ________. I would have made a complete fool of myself if I had said anything.      A. for; was discussed   B. of; had discussed   C. to; was being discussed  D. with; had been discussed   答案：C下列运算正确的个数是（　　）①（-10）-（-10）=0；②0-7=7；③（-3）-（+7）=-10；④56-（-16）=23． A、0B、1C、2D、3