问题补充：
The saying “Old friends and old wine are best” means the things and people we know are better than the unfamiliar.
A. what
B. which
C. that
D. who
答案：
A. what
B. which
(答案→)C. that
D. who
解析：考查从句，从句we know缺少宾语，which可以做宾语，但它有意义，表示哪一个，而句子没有这个意思；that只起引导作用，没有意义，所以选C
