He is very grateful to the girl he often turns for help when he meets with difficulties.
A. whom
B. to whom
C. to who
D. which
网友回答
A. whom
(答案→)B. to whom
C. to who
D. which
解析：考查定语从句：先行词是the girl，定语从句中turn后面少to和宾语，turn to求助于，介词后面只能接which或whom，不能接that或who，用to whom引导定语从句，句意：他对那个遇到困难时可以求助的女孩很感激。选B。