the middle of the 21st century , thevast majority of the world’s population ________ in cities rather than in thecountry

More than 60 million people in southwestern China ________the drought nowadays as a result of less rainfall, environmental damage and so on

We’ve just moved into a bigger house and there’s a lot to do. Let’s____it. [ ]

It’s time since we met last .

You shouldn’t talk until ________ to.