______ label to each of the trees, with detailed introduction of their features, and visitors will know more about them and how to protect them.
She can always create an atmosphere for her students, ___ allows them to talk freely with each other.
We are said to be living in ____ Information Age, ___ time of new discoveries and great changes.
—Hi, Terry, can I use your computer for a while this afternoon? —Sorry. ______
It was when she was about to go to bed ______the telephone rang.
When _____ to hand in his homework, Philip told his teacher that he had left it home.