To save class time,our teacher has ________ students do half the exercise in class and complete the other half for our homework.
.Play, often seen as______ activity for kids, is still important in____development of teenagers.
A big step____to strengthen China’s health care systems since we launched an effort in 2008.
.---Let me help you cross the street.--______! I’m not that old.
We went into a hall, on_____ walls hung a few pictures of some famous scientists.
Newly-developed materials for spaceships can _______ extreme weather conditions.