问题补充：
The river, the bank are covered with trees, is very long.
A. whose
B. which
C. of which
D. which of
答案：
A. whose
B. which
(答案→)C. of which
D. which of
解析：名词或代词+关系代词whom / which可以引导非限定性定语从句。表示部分与整体的关系，作用相当于whose+名词，of which the bank =the bank of which = whose bank, 因此答案为C。
