At times _______ exercise can make us _______.

She was greatly shocked at the scene before her eyes. Never did she expect that the local conditions ______ be so awful.

Every possible means ________ to prevent the air pollution, but the sky is still not clear. [ ]

Are you pleased with what he has done?— It couldn’t be ________. He must have put a lot of effort into his work.

Can Mr. King spare some time for the charity show–If he ___, he will try his best to make it.