Mr. Smith _________here for thre

Mr. Smith _________here for three weeks.
A、is already being
B、has already been
C、has already been being
D、is already
【正确答案】：B
【题目解析】：从for three weeks来判断直接用完成时,不用完成进行时 ,完成进行时强调他还会在这一直呆下去,因为没有语境,判断他是以前到现在呆,以后未必。