Her remarks left me wondering _______ she could have changed so

Her remarks left me wondering _______ she could have changed so suddenly.
A、when
B、how
C、whether
D、that
【正确答案】：B
【题目解析】：译文：她的话让我想知道她怎么变得这么突然。由句意可知，wonder后的宾语从句不缺由when引导的时间状语；whether引导的条件状语用在这里也不正确；that只是引导普通的陈述句，也不正确,答案为B。