积累与巩固 用所给单词的适当形式填空。 1.We are trying to work( (work)hard at all the subjects. 2.There used to be (be)a lot of manatees(海牛).But now there are few. 3.What was the air pollution caused (cause)by? 4.Have you ever thrown (throw)away things you don't like to use? 5.I have also set (set)up a website to sell clothes online. 6.Smoking is_harmful (harm)to your health.You must give it up. 导航页导航页 积累与巩固 用所给单词的适当形式填空。 1. We are trying __________(work) hard at all the subjects. 2. There used to __________(be) a lot of manatees(海牛). But now there are few. 3. What was the air pollution __________(cause) by? 4. Have you ever __________(throw) away things you don’t like to use? 5. I have also __________(set) up a website to sell clothes online. 6. Smoking is (harm) to your health. You must give it up. to work be caused thrown set harmful