The students _______to be at school at 8 am.

To save electricity, we are cutting down __________ our central heating.

What about ___________ the solution together this afternoon?

Let’s _________ water by turning off tapes when not using.

Without plants, most water ____________ off as soon as it falls, taking away valuable soil.

Both fossil fuel _______ non-renewable resources are very important to our life.

__________ we conserve natural resources, they will run out very soon.

Man and most animals need a _____________ supply of water to live.

The leopard is _________ the threat of extinction.

There are about 3,000 plants __________ values as medicines against cancer, AIDS, heart disease and many other sicknesses.

A hydroelectric dam ______________ in this area now.

I_______ in the lounge for ten minutes.

Deforestation _________ destroying Earth’s plant and animal variety.

Each year about fifty hundred_________ of plants and animals are already being eliminated.

Recycling is a good way of ___________ the environment.