The light will be thrown the cause of cancer by research that is now in progress.A. toB.

问题补充：

The light will be thrown the cause of cancer by research that is now in progress.

A. to

B. upon

C. in

D. for

答案：

A. to

(答案→)B. upon

C. in

D. for

解析：考查介词的用法。句意“正在进行的研究将对癌症的起因进行解释。”throw light on/upon sth.“解释，阐明”。故选B。