题干
——Mother's Day is coming. I've no idea______________for my mother.
——Hmm, maybe you can do the housework.
A：what I should buy
B：how should I do
C：what I should do
D：where should I go
答案(点此获取答案解析）
C
，该过程物体克服摩擦力做功为
。若小物块冲上斜面的初动能变为2E，则（ ）