问题
The old lady’s hand shook frequently.She explained to her doctor ______ this shaking had begun half a year before, and, ______ only because of this, she had been forced to give up her job.
A:when;how
B:how;when
C:how;how
D:why;why
B:how;when
C:how;how
D:why;why
正确答案是：
