I hope there will be ____ cars and ____pollution in the future, thus people will live longer.

This machine is very easy ______ Anyone can learn to use it in a few minutes

The president was so absorbed in his workthat not a sound ______.

The sound of the birds __________happy memories of my childhood holidays.

Theteachercouldn’tmakehimself_____attentiontobecausethestudentsweresonoisy [ ]