Ann is a careful girl．She always goes over her exercises to ____ here are no mistakes．

If you are weak ____ a subject, ______your teacher for advice can help.

I called you yesterday evening, but there was no answer.—Oh, I am sorry I _____dinner at my friend’s house.

What do you think of the color of my bedroom?—Sorry, but what did you say? I ________ about something else.

It is too noisy. I can hear what Mr. Wang is saying.