It is the prevention of disease_____ itssuccessful treatment that has led to the rapid increase of the world’spopulation

Earth is believed ____ by an object the size of Mars at some point in the distant past before its surface cooled.[ ]

I decided to follow it to see _________.

Can you hear me–No, I can’t. Would you please speak .

Since___1980s, the new technology has been used on trains in _____Europe.