第一题选B,句子变成These books of which he read some were written by Lu Xun. which 引导定语从句of which he read some修饰先行词these books, 把of which 还原到从句中,变成he read some of which (these books),意为,他读过这些书中的若干本.
第二题选B,which 引导非限制性定语从句which I can reach most evenings.原句中打多了一个be. which 指代的就是先行词my friend's home address(我朋友的家庭住址).因为主句中并没有体现时间,所以引导词不必考虑when.