根据短文内容，从A、B、C、D四个选项中选择一个最佳答案．

With the development of technology，bicycle sharing comes into people's lives．In big cities shared bikes like Mobike and Ofo （21） 　　more and more popular in the past two years．They bring great convenience for people traveling．You can find a bicycle （22） 　　at anytime when you want to go out for a cycling．If you have a smart phone，what you do is to find the （23） 　　shared bike，scan the QR code（扫描二维码）on the bike through the APP，and enjoy your trip．They can take you where the subway and the bus don't go．And they （24） 　　anywhere in public for the next user．（25） 　　，along with its fast development，there are some problems caused by bicycle sharing．Some people damage（毁坏）the QR code onthe bike，（26） 　　use their own locks，which causes trouble to other users．What's more，kids can open the lock and ride the bicycle （27） 　　．There's no doubt that it is very dangerous．（28） 　　bicycle sharing brings so many problems，it is really helpful to us as a high﹣tech product．So we should take a developing opinion about bicycle sharing．On the one hand，everyone should （29） 　　public services．On the other hand，our government should regulate（规范）this market （30） 　　good use of its advantages．

21．A．became	B．have become	C．become	D．has become
22．A．somewhere	B．nowhere	C．anywhere	D．everywhere
23．A．nearest	B．farthest	C．nicest	D．fastest
24．A．must be sold	B．can be left	C．must be ridden	D．can be given
25．A．Instead	B．Almost	C．Anyway	D．However
26．A．but	B．for	C．or	D．so
27．A．easily	B．early	C．slowly	D．luckily
28．A．Because	B．Although	C．When	D．As
29．A．take after	B．take good care of	C．take place	D．take action
30．A．make	B．making	C．made	D．to make