Oxygen is needed for combustion.

Everyone called out to the singer for an encore.

Scientists are fighting to stem the spread of the AIDS virus.

Science and technology have come to pervade every aspect of our lives and, as a result, society is changing at a speed which is quite unprecedented.

The rent is due tomorrow.

How much is the rent per month?

His whole family is like that. They're like peas in a pod.

The members of the family nursed the patient by turns.

I mortgaged my house.

We'll use the house as collateral so we can borrow some money.