如下图所示，某植物上的绿叶经阳光照射一段时间后，经脱色并用碘液处理，结果有锡箔覆盖的部位不呈蓝色，而不被锡箔覆盖的部位呈蓝色。本实验证明

①光合作用需要二氧化碳 ②光合作用需要光 ③光合作用需要叶绿素 ④光合作用放出氧气 ⑤光合作用制造淀粉[ ]

A．①②

B．③⑤

C．②⑤

D．①③

The old lady's hand shook frequently. She explained to her doctor_______this shaking had begun half a

year before, any ____, 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