The world economic crisis _______ in 2008, but the global economy began to recover in the second half of 2009.
It was ______ the second-hand bus that the mechanic spent the whole afternoon in the factory.
He doesn’t think the question of ______they are boys or girls is important .
Great changes have taken place in that school. It is no longer _____it was 20 years ago, ______it was so poorly equipped.
A forest is usually found _______ heavy rainfall is frequent.
—When can I use your computer? —Never! _______ should you touch it.