--- The two old friends were ______ busy _____with each other ______ the time.--- Yes. They haven’t met for long.
Let him _________. Don’t make him __________.
_________ the animals _________ our duty.
We are making a plan _________ water clean.
Let’s _________ what we can do to save the animals in danger.
--- How can you _________ there? --- ___________air.