Решение:
- Deserts are the driest places in the world. (Past Simple: Deserts were; Present Simple: Deserts are)
- Different seaweeds lived (to live) in the oceans many years ago. (Past Simple: lived)
- Salty sea covered (to cover) more than half of the world. (Past Simple: covered)
- The weather is wet now. Helen wears (to wear) her new raincoat. (Present Simple: wears)
- These plants grow (not / to grow) high up in the mountains. (Present Simple: grow)
- The weather is (not / to be) dry in the jungles. (Present Simple: is)
- Big animals live (not / to live) in the grasslands. (Present Simple: live)
- Little Tom swam (not / to swim) in this deep lake last summer. (Past Simple: swam)
- Last month we were (to be) at the zoo and saw (to see) eagles. (Past Simple: were, saw)
- What are you doing? - I am watching (to watch) cartoons. (Present Continuous: am watching)
Ответ: 1. are; 2. lived; 3. covered; 4. wears; 5. grow; 6. is; 7. live; 8. swam; 9. were, saw; 10. am watching.