30. Even if you are an experienced teacher, you sometimes ____ make some mistakes.
I’m happy ______ should be done has already been done.
The old man believes that his neighbor who smokes _____ for the big fire.
We always lose sight of those who adore(爱慕) us, adore those who ___________ us, and hurt those who love us.
The old man __________ many dangers during the war. He said he narrowly escaped death.
He _________ to curiosity and opened the letter secretly.