In the dark street there wasn’t a single person Mary could turn for help.A. to whomB. to

问题补充：

In the dark street there wasn’t a single person Mary could turn for help.

A. to whom

B. to which

C. on whom

D. on which

答案：

(答案→)A. to whom

B. to which

C. on whom

D. on which

解析：考察定语从句，该句为定语从句， 先行词是single person, 在从句中作turn to的宾语，turn to sb for help意为向某人求助，to 是介词，后面指人的时候只能选择whom，所以选择A