Most birds find it safe to sleep in the trees, but ____ they have eggs or young chicks, they don’t use a nest.
| A．why | B．how | C．unless | D．where |
31. To our surprise, they decided to________their differences and try to face the coming global problems together.
| A．give away | B．take up | C．put aside | D．bring down |
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 |