Who taught ________ to write the computer programs? —Nobody. She learned it by __________.

If I want to see them at the weekend, I just walk __________ to their houses.[ ]

I don’t know the man _______ is looking after the old woman.

Do you like the hero ______ fights for freedom all the time in the book?—Yes, of course. I think he is great.

A：Who（谁）is that girl?B：Oh, is my friend. name is Sally.