The air is deadly polluted because some factories don't ________ the rules to protect the environment.
There are two buildings, __________ stands nearly a hundred feet high.
Tony can hardly boil an egg, still __________ cook dinner.
It may not be a great suggestion. But before __________ is put forward, we'll make do with it.
There are a small number of people involved, possibly __________ twenty.
Next to biology, I like physics __________.