While watching television, ________.
| A．the doorbell rang | B．the doorbell rings |
| C．we heard the doorbell ring | D．we heard the doorbell rings |
30.________some English-learning websites if you are free, and you will learn a lot about how to study English.
| A．Having visited | B．To visit | C．Visiting | D．Visit |
29. My father, who values honesty__________all things, never allows us to tell lies.
| A．within | B．despite | C．throughout | D．Beyond |
28. It is only when agriculture is fully developed___________industry can have abundant materials and markets.
| A．that | B．when | C．before | D．Until |
27. Though____________of the danger of walking alone in the street at night, he wouldn’t have anyone accompany him.
| A．warning | B．being warned | C．warned | D．having warned |
26. The professor was asked to write an article for the newspaper, ___________about the left-behind children in the countryside.
| A．any | B．one | C．that | D．It |