Thomas the army for two years so he misses his mother very much. A.has joined B.has taken

问题补充：

Thomas the army for two years,so he misses his mother very much.

A.has joined B.has taken part in C.has been in

答案：

解析：本题的含义为汤姆斯参军已经2年了，表示时间长度，不可以使用短暂动词join或take part in，可以用be in来表示，故本题选B。