Did you catch the train to Beijing last night?— No. It ______ for ten minutes by the time I got to the station.

Is the girl in the red skirt your sister?—No. She is____ classmate.

What do you ____________ your English teacher? — Wow, she’s very friendly.

What do you think of the report about the air pollution on TV last night?—I think the situation is so that we should take action to protect the environment.

It was a serious mistake, ______ caused by carelessness.