1.Skycycling tubes will be easy to drive.( It)
2.My bike is green.( mine)
3.Do flying cars interest you? (interested)
4.It isn't a good idea to go such a long way by bike.(should)
5.Electric cars cause no air pollution,but they still cause traffic jams.(Although)
6.Sue is talking to a friend of hers.( her)
7.When I was in secondary school,I usually walk to school.(foot)
8.They will use GPS technology to increase accuracy and shorten routes.(used)