（-1）2的相反数是______．
∵（-1）2=1，1的相反数是-1，∴（-1）2的相反数是-1．
— I promise my daughter _____ get a nice present on her birthday.
— I think it will be a big surprise to her. [ ]
A. must
B. shall
C. might
D. need
背散射电子
