If you live in Changchun, you may notice that the air in winter is not as _______as it is during the summer.

A.clean B.cleaner C.cleanest D.cleaning

A friend of ________ named Paul received a new bicycle from his brother as a Christmas gift.

A.I B.my C.mine D.myself

Wu Dajing broke his own record and _______the gold medal（奖牌）in the men's 500-meter race.

A.win B.won C.winning D.wins

Our memories can ________ or even forgotten completely.

A.change B.changed C.are changing D.be changed

There ________ no mountain on the earth that can grow taller than Qomolangma.

A.be B.am C.is D.are

The police ________ early on foot in order to find the truth behind the mystery.

A.cut out B.found out C.set out D.blew out

_________ it was hard to keep up with the online classes, I tried my best to follow them.

A.Whether B.However C.Because D.Although

I thanked my Chinese teacher _________ helped me get through the test.

A.which B.what C.who D.where

_________, the Chinese government has done a lot of work, including building roads and providing better education.

A.Help the poor B.Helped the poor

C.Helping the poor D.To help the poor

— I know that one of the 2019 Nobel Prize winners in chemistry is almost 100 years old.

— ________ hard-working and creative the person is!

A.How B.What C.How a D.What a