问题补充：
We can’t work out the physics problem. Can you tell us ?
A. how to do
B. what to do it
C. how to do it
D. what should to do
答案：
A. how to do
B. what to do it
(答案→)C. how to do it
D. what should to do
解析：句意：我们不能算出这道物理题，你能告诉我们怎么做吗? how 指方式,how to do it,怎么做，it做宾语，不能省; what 指内容, what to do it 错了, what 已经做宾语了，要去掉it.。故选C。
