ather in Inner Mongolia is always dry, butsometimes it _____ rain heavily

To discuss “population as a global __________ ”, we are supposed to know about the history of population trends.

____interesting experiment it is!

do you find the town you visited yesterday— The town has changed out of all ______ in the past 20 years, acompletely new one in front of me.

I admire Stephen Hawking greatly，whose________about black holes has a great effect on astronomy.