More and more high-rise buildings have been built in big cities __________ space.
Some experts warn that global wanning will______more than one million sorts of plants.
The company had to______a number of workers because of the drop in sales.
Billy was the youngest boy on the hike, but he______with the others.
You’d better wash the shirt in cold water, or the color will______.
We have to______the costs of the new system against the benefits it will bring.