thanks,xuyi.
BTW, don't u think the RC in Case 1should be a restrictive one in which the comma should be crossed out?
This is what Lin (2004) suggested (p.55 right column)
See 中国学生英语写作中的从句错误 林德华 解放军外国语学院学报 2004 3
http://www.corpus4u.org/upload/forum/2006040811462913.rar