In the last few years,China ___ great achievements in environmental protection.
| A．has made | B．had made |
| C．was making | D．is making |
The best times to visit Shangri-la are spring and autumn ____ the temperature is at its mildest.
| A．when | B．where | C．that | D．which |
Scientists study ____ human brains work to make computers.
| A．when | B．how | C．that | D．whether |
______ in the school campus in spring, we will always noitce a colorful display of flowers.
| A．Walk | B．Having walked | C．Being walking | D．Walking |
It’s great that all the visitors who _______ on the island were saved.
| A．trapped | B．have been trapped | C．had trapped | D．had been trapped |
The operation is _______ success. and the patient is now out of ______ danger.
| A．a; the | B．/ ; / | C．/ ; the | D．a ; / |