That evening, _____ I will tell you more about later, I ended up working very late.

A．that

B．which

C．what

D．when

薯蓣皂苷的苷元母核结构类型是（）

A.螺甾烷

B.异螺甾烷

C.四环三萜

D.五环三萜

E.达玛烷