HelenandMaryaregoodfriends.

问题详情：

Helen and Mary are good friends. _______often help each other.

  A. Them         B. Theirs           C. They            D. Their

【回答】

C

【解析】人称代词的用法。they 代替前面所指的Helen and Mary，在句中作主语，用主格。故选C.

知识点：人称代词

题型：选择题