22. (2014·南通高一检测)At present, we are studying a total of nine subjects, ______I think is physics.
A. of them the most difficult
B. and the most difficult of which
C. the most difficult of them
D. the most difficult of which
【解析】选D。考查定语从句。句意: 现在我们总共学习9门课程, 其中我认为物理是它们之中最难的。which引导非限制性定语从句, 修饰先行词subjects, 相当于并列句and the most difficult of them I think is physics。
