【题目】They had no choice but ______ as their mother told them.
A.do
B.to do
C.doing
D.done

【答案】B
【解析】考查固定句式。句意：他们别无选择只能按照母亲告诉他们的去做。have no choice but to do“除了做…别无选择”，故选B。