turn around
well done
3.know....well4.all the year around
8.have a space journey
9.space station
10.do an experiment
11,have own water supply and oxygen supply system
13,in this way
14,go on a trip
15,in the 21st century
16.have?something belonging to self
18.in the space
19,in the sky
20,in the desert
21,How much is the earth's surface covered with water ?
22.How much is the land surface covered with desert?