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2. Everyone should learn to ________ (conserve/Converse ) energy.
3. Nancy is ________ (cornered/concerned) about pollution. This is why she walks
to work instead of driving.

4. (Baking/Biking) ________ is much healthier than driving, and it doesn’t pollute
the air.

5. David conserves water by not letting it ________ (run/jog) when he’s not using
it.

6. I’d like to conserve water... But I feel dirty if I don’t ________ (bath/ shower)
three times a day!
7. Many unethical companies ________ (dump/give) their waste into rivers.

8. (Smog/Smoke) ________, which is partly caused by exhaust fumes from cars, is
a very big problem in many big cities across the world.

9. (Dirty/ Acid) ________ rain occurs when pollution in the air is absorbed by water
droplets in clouds.
10. Oil ________ (soil/spills) pollute sea water and kill marine life.

Mastering Grammar

• Modals
We use modals to show if we believe something is certain, possible or impossible:

For example, My keys must be in the bag.
It might not rain tomorrow.

We also use them to do things like talk about ability, ask permission, and make
requests and offers:
For example, I can swim.
May I ask a question?

• Here are some characteristics of modal verbs:

1. They never change their form. You can’t add “s”, “ed”, “ing”...
2. They are always followed by an infinitive without “to” (i.e. the bare infinitive.)

3. They are used to indicate modality and allow speakers to express certainty,
possibility, willingness, obligation, necessity, ability

• Complete the sentences with a modal verb from the box below. Sometimes more
than one answer is possible.

Can, can’t, can’t have, could, could have, don’t have, had better, might, must

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