46. Why does the professor mention the photograph of the painting Corn Belt City?
47-50 A radio report about scientific advance.

Did you know that vegetables can be tricked into growing in the 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 are living in cooler climates. That way they grow faster and taste better. What these engineers have been using is very simply cold sea water. How did they use it? They place pipes in the soil and cold water flowing through them cools the earth. This 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 gardens. What is 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 west coast of the United States could be air-conditioned using sea water. We ll be back to discuss that possibility after this commercial message.
47. What is the report mainly about?
48. What does the new system enable the farmers to do?
49. How were the pipes used in Hawaii?
50. Why does the speaker mention air-conditioning?

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