Livemocha. is a free site visitors can not just learn various languages but also chat online.
A. where
B. which
C. that
D. what
网友回答
(答案→)A. where
B. which
C. that
D. what
解析：此处a free site是先行词，其在定语从句中作地点状语，故选A。句意：网站Livemocha.是一个免费的网站，在这个网站访问者不仅能学习各种语言而且可以网上聊天。