复习动词的语态，即主动语态和被动语态。

1. 动词语态的复习

语态是表示主语与谓语的关系的。如果主语是动作的执行者，动词要用主动语态，反之，如果主语是动作的承受者，动作就要使用被动语态。

被动语态的结构：be + 动词的过去分词。

9. Some of the swamps have become polluted. 一些沼泽地已经受到污染。(现在完成时)

8. In 1972, it was discovered that they were endangered. 1972年发现海牛濒临灭绝。(被动语态)

7. There used to be a lot of manatees. 过去有许多海牛。(used to 一般过去时)

6. Manatees eat about 100 pounds of food a day. 海牛每天要吃100磅左右的食物。(一般现在时)

5. We’re trying to save the manatees. 我们正在尽力挽救海牛。(现在进行时)

4. I think that…我认为…

I believe that…我相信…

I feel that…我觉得…

3. I agree / disagree with you. 我同意/不同意你的意见。

2. I like pandas best because they are so cute. 我最喜欢熊猫了，因为它们太可爱了。

1. Manatees are gentle. 海牛很温顺。