As teenagers of the 21st century, we should be ready to _____ the challenge of society.
. Man must produce more grain to support the _____ growing population on earth.
The theory wasn’t accepted by many people when it was first ____, but it proved to be true as time went by.
He is good at maths and it won’t be long ____ he works out the problem.
—Learning a language isn't easy. It takes time. —I agree. _______. There's no short cut.
His knowledge of French is ___________ for the job, although he was not fluent in the language.