Zhaozhou Bridge is one of stone bridges in the world．（ ）
A．oldB．olderC．oldestD．the oldest
﹣ did you write to last night？﹣A pen pal．（ ）
A．WhatB．WhereC．Whom
She is listening to music he is doing his homework．（ ）
A．afterB．beforeC．while
He is at English than me．（ ）
A．goodB．betterC．best
It's our duty our hometown clean and beautiful．We must do something for it．（ ）
A．keepingB．keepsC．to keep
I have friends，so I feel sad．（ ）
A．fewB．a fewC．little