1 . while引导的让步状语从句
尽管我承认这个问题很难，但是我并不认为无法解决。(汉译英)

2 . Most teachers believe that students ________ to experiment with new ideas.

A．must encourage

B．should be encouraged

C．can encourage

D．might have encouraged

3 . No child under 12 is allowed to go to the lake alone; any walk close to the lake ________by a parent.

A．must be accompanied	B．must accompany
C．can be accompanied	D．should accompany