一Professor Li, ______the student start at once or wait a while? 一At once.
The teacher asked us _______ so much noise.
—How do you deal with the disagreement between the company and the customers? —The key _______ the problem is to meet the demand _______ by the customers.
In order to make our city green, _______.
In order not to be disturbed ,I spent three daysin my study.
He sat back on the chair, took a book and began to read, ___.