She _____ have left school, for her bike is still here.[ ]

Living in the central Australia desert has its problem, _____ obtaining fresh water isn’t the least

.—Jim!Did you have a good time at the party?—Yes,but I really _________ have because I had a lot of work to do.

What do you think of_______ tour around our city—– Oh, what_______ different Yangzhou! I like itvery much.

If we use new types of energy， they will produce little pollution. ______ they cost very little and never run out.