—_______ they _______ the book _______ to the library yet?
—Yes, they have.
A. Have； returned； / B. Have； returned； back
C. Did； return； / D. Did； return； back
He _______ until it began to rain.
A. didn’t stop working B. didn’t stop to work
C. stopped to work D. stopped working
The old lady didn’t know _______ when the house caught fire.
A. how to do with it B. how to do
C. what to do D. what to do it
He will use what he has _______ her a new dress. Her birthday is coming.
A. bought B. to buy
C. buying D. been bought
They _______ the train until it disappeared (消失) in the distance (在远处).
A. saw B. watched C. noticed D. realized
We work together to achieve our common purpose： ________ world that is safer, cleaner and healthier than ________ one we are living in.
A. the ； / B. a ； /
C. the ； the D. a ； the
