【正确答案】
B
【答案解析】[听力原文]
Did you know that vegetables can be tricked into growing in climates they are not accustomed to? Cool climate vegetables like asparagus are now able to be grown in places as hot as Hawaii. In Hawaii, marine engineers have been able to actually convince such vegetables that they"re in cooler climates. That way they grow faster and taste better. What these engineers have been using is very simple —cold water. How do they use it? They place pipes in the soil and the cold water flows in through and then cools the air. This new system stimulates plant growth and enables gardeners in tropical climates to grow crops from cooler climates. Also some of these pipes are exposed to the air and they condense moisture and thus irrigate the garden. What"s especially appealing about this process is that nothing damaging to the natural environment is being used. Another innovative use for cold ocean water is to cool buildings. Engineers believe that, for example, the entire western coast of the United States could be air-conditioned using seawater. We"ll be back to discuss that possibility after this commercial message.
What is the passage mainly about?
[解析] 本文主介绍了有关农业灌溉方面的一些知识，属于科普知识类题材。
短文前半部分主要介绍通过冷海水在管道中的流动，使非热带作物得以在热带环境下生长，后半部分介绍了冷海水的另一个用途：使建筑物内变得凉爽。由此可知本文主要讲了冷海水的用处，故答案为B。