Scientists in Israel have discovered a new way to test for water pollution by “listening”

Scientists in Israel have discovered a new way to test for water pollution by “listening” to what the plants growing in water have to say.
By shining a laser beam (激光束) on the tiny pieces of algae floating in the water，the researchers said they hear sound waves that tell them the type and amount of contamination (致污物) in the water.
“It is a red light，telling us that something is beginning to go wrong with the quality of water，” said Zvy Dubinsky，an aquatic biologist at Israel’s Bar Ilan University.“Algae is the first thing to be affected by a change in water quality.”“The secret，” he said，“is to measure the rate of photosynthesis (光合作用) in the algae，meaning the plant’s ability to transform light into energy.” During photosynthesis，plants also release oxygen into the air.
Dubinsky’s technique is easy to perform because of the over­abundance of algae in the planet’s water.Most of the oxygen in the atmosphere comes from algae.A prototype tester that occupies about one square meter of a laboratory desktop，shoots a laser beam at water samples to stimulate photosynthesis in the algae.But not all of the laser’s heat is used.Depending on the condition of the algae and the rate of photosynthesis，some of the heat is shot back into the water，creating sound waves，Dubinsky said.With a special underwater microphone，researchers are able to analyze the strength of the sound waves and determine the health of the algae and the condition of the surrounding water.
“Algae suffering from lead poisoning，like waste discharged from battery and paint manufacturing plants，will produce a different sound than those suffering from lack of iron or exposure to other toxins，” said researcher Yulia Pinchasov.She said that testing algae photosynthesis can determine water quality more accurately and easily than labor­intensive methods now used like chemical and radioactive carbon testing.
【小题1】The underlined word “algae” in Paragraph 2 probably refers to a kind of .A．instrumentB．plantC．woodD．pollutant【小题2】Why is the algae tested?A．Because it floats on the water.B．Because it can have photosynthesis.C．Because it is the first to be polluted.D．Because it can produce different sounds.【小题3】We can infer from the passage that .A．algae can produce a loud sound when pollutedB．algae can die easily from pollutionC．photosynthesis of the algae can only be caused by sunlightD．photosynthesis of the algae is related to water quality【小题4】What would be the best title for the passage?A．Scientists Listen to Plants to Find Water PollutionB．A Prototype Tester Is Used to Determine Water PollutionC．The Importance of Photosynthesis of the AlgaeD．The Problem of Chemical and Radioactive Carbon TestingB

(答案→)B 解析：【小题1】　B解析　词义猜测题。由文章第一句中的“what the plants”及第三段倒数第二句中“meaning the plant’s ability to transform light into energy”可推出，algae是一种植物，因为只有植物才能进行光合作用。【小题2】　C解析　细节理解题。由文章第三段第二句可知，藻类是水中最先受到污染的植物，因此科学家用它来研究并判断水的污染情况。【小题3】　D解析　推理判断题。由文章最后一段可知，通过检测藻类的光合作用可以确定水的质量，因此藻类的光合作用跟水的质量有密切关联。【小题4】A解析　主旨大意题。概括全文可知，本文主要讲了科学家通过探听水中植物的状况来发现水污染的程度。文章第一段就点明了主旨。

我也是这个答案