单项选择(每题1分)He often speaks of the trouble he _______ to help the orphan.
once before, after your class I got my visa(签证). So thank you again.
Who is the man a blue shirt? I have never seen him before.
Here is my classmate ________ bicycle was lost yesterday.
The young doctor is determined to devote all his life to ________ the cause of cancer.
This dictionary ________ me. It cost me twenty dollars.