Suppose you find a bright yellow bike on a street corner in the city．You hop on（跨上）it and （31） 　　．But wait﹣isn't this stealing？No，it isn't．（32） 　　shouts，"Stop!Thief!"That is （33） 　　this free ride is just fine with the city．

You（ 34） 　　for （35） 　　transportation，and they wanted to help （36） 　　

pollution．So，to get citizens（市民） （37） 　　their cars and onto pollution﹣free bikes，they （38） 　　the Yellow Bike Project．

The （39） 　　bikes are painted bright yellow and placed throughout the city．People can hop on the yellow bike and ride to run errands（短程差事），to work （40） 　　to school．Then，they leave the bike for the （41） 　　rider．There have been times when bikes have been stolen，but most people （42） 　　the rules，because they think it is not wise to （43） 　　the bike that's already free．

Portland's （44） 　　was quickly loved by a lot of people．Within two years of its starts，similar programs were （45） 　　in cities in six other states．

31．A．drive away	B．ride away	C．ride back	D．run away
32．A．No one	B．Someone	C．Anyone	D．Everyone
33．A．whether	B．so	C．because	D．though
34．A．have to	B．don't have to	C．can't	D．can
35．A．expensive	B．crowded	C．free	D．common
36．A．protect	B．control	C．make	D．bring
37．A．out of	B．into	C．up	D．near
38．A．ended	B．started	C．changed	D．refused
39．A．public	B．private	C．clean	D．dirty
40．A．but	B．as	C．until	D．or
41．A．next	B．last	C．best	D．first
42．A．break	B．make	C．discuss	D．follow
43．A．buy	B．repair	C．produce	D．steal
44．A．citizen	B．street	C．idea	D．school
45．A．looked up	B．made up	C．put up	D．set up．