与人类皮肤癌有关的致癌物是（）。

A.紫外线

B.黄曲霉素和植物苏铁素、乙型肝炎病毒

C.EB病毒

D.血吸虫病

E.单纯疱疹Ⅱ型病毒

(2013·湖南高考)He ________ sleep, although he tried to, when he got on such a hunt for an idea until he had caught it.

A．wouldn't

B．shouldn't

C．couldn't

D．mustn't