1)young people perfect the city because it has many places of....
a.entertainment b.environment  c government
2)do you think humans will live ..the moon
a. at b.in c on
3)in the video clip,the astronaut is...around on the space station
a. floating b.flying c flowing 
4)each student should..up the garbage and put it in the garbage can
a.take b pick c lift
5.the musicans arried..a taxi
a by b.in c.on
6.this area is a perfect place for those who love rock...
a climping b hiking c rafting
7)remember to clean up before you....the campsite
a visit b reachc leave