The traffic slowed down because of the heavy snow in Yushu County, presenting a new _____ to the discovery from the earthquake.
| A．suffering | B．disaster | C．damage | D．challenge |
The poet andpianist is going to give us a talk this afternoon.
| A．a | B．the | C．不填 | D．an |
We can never expect ____ bluer sky unless we create _____less polluted world.
| A．a; a | B．a; the | C．the; a | D．the; the |
Would you like tea or coffee?
--_____, thank you. I’ve just had some water.
| A．Either | B．Both | C．Any | D．Neither |
In that school, English is compulsory for all students, but French and Russian are ______.
| A．special | B．regional | C． optional | D．original |
Sometimes proper answers are not far to seek ______ food safety problems.
| A．in | B．to | C．on | D．after |