1891年，美国颁布《森林保护法》，授权总统划留林地。西奥多·罗斯福接任总统后，制定垦荒法，设立土地开垦局，修建十个大型水坝，创建了五个国家公园，五十多处野生鸟类保护区等。1908年，成立国家资源保护委员会，以保护全国的水源、森林和矿产资源。1933年，美国国会通过了《田纳西河流域管理局法案》，成立了田纳西河流域管理局，对流域内的自然资源进行全面的管理和综合开发。同一年，美国建立平民自然资源保护队，雇佣275万失业青年从事造林和水土保持等工作。

结合材料和所学，概括历史上美国为保护环境所采取的措施及其特点。

补全对话。

Peter: Hi, Eric. ____

Eric: It was great!

Peter: Did you go to the zoo?

Eric: ____ I went to a farm. look, here are my photos.

Peter: Did you see any cows?

Eric: Yes, I did. ____

Peter: Did you ride a horse?

Eric: No, I didn't. But I milked a cow.

Peter: ____

Eric: Well, I saw some chickens but I didn't feed them.

Peter: ____

Eric: My friends and I went for a walk around the farm and talked with a farmer.

A: Hi, Linda, ____

B: Hi, Mary! Happy birthday! Here is a present for you.

A: Oh, it's very nice of you.  ____

B: Guess (猜).

A: Is it a new schoolbag?

B: ____ Open (打开) it and you will see.

A: Wow！ A blue skirt.

B: ____

A: Yes, I love it. Thank you so much.

B: ____

         --Yes，I do．I should go home because my flowers need         ．