Question

With petroleum reserves (石油储量) decreasing, the search is on to replace gas with a cleaner，greener alternative. Though much eco－talk has centered on biofuels from corn and soybeans, the biofuel that looks more likely to replace petroleum comes from a most unlikely source: algae(藻类)．

Algae, like corn, soybeans, and other crops, grow via photosynthesis(光合作用) and can be processed into fuel oil. However, they yield 30 times more energy than land crops such as soybeans, according to the U．S. Department of Energy. Many algae species also can grow in saltwater and polluted water—while corn and soy require arable land and fresh water that will be in short supply as the world's population balloons.

“If you replaced all the diesel(柴油) in the U．S. with soy biodiesel, it would take half the land mass of the U．S. to grow those soybeans，” says Matt Caspari, chief executive of Aurora Biofuels, a Berkeley, Calif－based private firm that specializes in algae oil technology. On the other hand, the Energy Department says that if algae fuel replaced all the petroleum fuel in the United States, it would require 15,000 square miles, which is a few thousand miles larger than Maryland (12,407 square miles), the 42nd state in land area.

Another bonus: Because algae can be grown just about anywhere in a closed space, they're being tested at several power plants across the nation as a carbon absorber. Smokestack emissions (烟囱排放物) can be pumped directly into the ponds, feeding the algae while keeping greenhouse gases out of the atmosphere.

Although processing technology for algae fuel－also known as “oilgae” in some environmentalist circles—is improving, it's still years away from reaching your local gas pump. “It's just a question of cost, because no large－scale facilities have been built yet，” Caspari says.

1. The underlined word “yield” in Paragraph 2 can be replaced by ________.

A. control         B. require

C. produce         D. grow

2. Compared with corn and soybeans, algae________.

A. may pollute water and soil

B. can grow in poor conditions

C. provide much less energy

D. need more special care

3. According to Paragraph 3, one of the advantages of algae fuel is that________.

A. it can be used more widely

B. it is more easy to produce

C. it needs much less land

D. it costs much less money

4. What do we learn about algae from Paragraph 4?

A. Algae help protect the environment.

B. People can grow algae anywhere.

C. Fish can get more oxygen from algae.

D. Algae produce less waste.

5. What does the passage mainly talk about?

A. Environmental protection.

B. Biofuels from corn and soybeans.

C. The false hope of biofuels.

D. A promising oil alternative.

Answer 1

1. 解析：选C。词义理解题。此处根据这句话的意思可以推出它们生产的能量比大豆之类的农作物要多30倍。故选C。

2. 解析：选B。细节推理题。根据第二段第三句的“...can grow in saltwater and polluted water”和“...require arable land fresh water...”可知，玉米和大豆需要有良好的环境才能生长，而藻类在较差的环境下也能够生长。

3. 解析：选C。细节理解题。根据第三段最后一句“On the other hand... the 42nd state in land area”可知，如果藻类燃料全部代替美国的石油燃料，所需土地比马里兰州的面积多一些，而该州面积仅居全美国42位。联系本段第一句的“...it would take half the land mass of the U．S. to grow those soybeans...”可知，生产藻类燃料仅需很少的土地。

4. 解析：选A。推理判断题。根据第四段第二句“Smokestack emissions can...of the atmosphere”可知，烟囱排放物能够直接排入养殖着藻类的池塘，既向藻类提供了养料，又防止了温室气体污染大气。可见，藻类对保护环境有利。

5. 解析：选D。主旨大意题。本文介绍了一种颇具前景的藻类能源，重点分析了这种新能源的优势。注意第一段第一句的关键词alternative。