The old lady’s hand shook frequently. She explained to her doctor _______this shaking had began half a year before, and ______, only because of this, she had to give up her job.

A．when; how

B．how; when

C．how; how

D．why; why

中外合作企业的合作各方应在法定期限内缴付出资，该法定期限是合同签订后6个月内。( )