1 . If you want to get a better grade in math, you should correct your mistakes ________ and learn from them.

A．in time

B．by mistake

C．at first

2 . She wrote down some notes on a piece of paper, but her mother threw it away ________ mistake.

A．in

B．at

C．by

D．of

3 . The woman took my bag ________ mistake.

A．for

B．at

C．of

D．by

4 . 你知道薯条是无意中被发明的吗？
Do you know potato chips were invented ________?

5 . I took your bag instead of mine ________ (错误地).

6 . —Joseph, did you break the glass?
—I’m sorry, but I didn’t do it ________.

A．on purpose

B．in public

C．by mistake

7 . 有人错拿了我的包。
Someone took my bag ________.

8 . Tony上周五错拿了我的雨伞。
Tony took my umbrella ________ last Friday.

9 . —You look very happy. What happened?
—I met my first English teacher ________ in the street. I haven’t seen her for eight years.

A．in public

B．by mistake

C．by accident

10 . I took Tony’s cap ________ mistake.

A．by

B．for

C．in

D．at