问题
选择题
At last the mother had no choice but ___________ her son herself, though she was quite busy．
A．to pick up
B．pick up
C．picking up
D．picked up
答案
答案：A
固定结构：had no choice but to do sth 别无选择只有…。 最后妈妈别无选择只有背起孩子尽管她很忙。