BEIJING is the capital of China.It was very clean and beautiful in the past.

BEIJING is the capital of China.It was very clean and beautiful in the past.
BEIJING is the capital of China.It was very clean andbeautiful in the past.31 ,it has been suffering 32 smog（雾霾）now and then.Lastmonth there were only five 33 free of smog.Some people even say BEIJING is one of the 34 cities in the world.Nowadays people begin to 35 the PM2.5 report and long for winds more thanbefore.You will also find the people in BEIJINGnow not only take the keys,wallets,cell phone 36 also take a face mask.They hope it can protectthem from the polluted 37 .Some students at No.4 High School spent2 days completing a 70000-word report.They suggested schools should consider 38 outdoor activities when PM2.5 numbers are toohigh.They believe more people will join them in making a 39 .The blue sky will certainly 40 and stay.
31.A.Whatever B.Wherever C.However D.Whenever
32.A.from B.in C.on D.of
33.A.minutes B.seconds C.days D.months
34.A.dirty B.dirtiest C.clean D.cleanest
35.A.touch B.listen C.see D.notice
36.A.so B.and C.but D.that
37.A.city B.air C.cloud D.rain
38.A.to end B.ending C.ends D.end
39.A.difference B.difficulty C.destroy D.disagreement
40.A.turn B.disappear C.leave D.return