题目

I decided to play a joke ________my sister ________April Fool's Day. A . at; at B . on; on C . at; on D . on; at 答案：B计算：（1）-24+3.2-16-3.5+0.3；（2）0-2123+(+334)-(-23)-(+0.25)；（3）4×（-12）+（-5）×（-8）+16；（4）34×(8-113-1415)；（5）-3.5÷78×(-34)；（6）(150-1)(149-1)(148-1)…(14-1)(13-1)(12-1)．