He helps his friends their English.A. in B. at C. with

问题补充：

He helps his friends their English.

A. in B. at C. with

答案：

解析：in在里面；at在一点；with带有，伴随，对于。句意：他帮助他的朋友学习英语。短语help sb with sth帮助某人做某事，故选C。