—If I were you, I ______ for it last night instead of watching movies.
A：would prepare
B：prepared
C：had prepared
D：would have prepared
设Sn是等差数列{an}的前n项和，若 a5a3=59,则S9S5 =（ ）
输入2×（﹣1）+3，输出____ ．
二项式 x-1x9的展开式中 x3 的系数是（ ）
