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Israeli researchers say they have developed a substance that attracts and kills the mosquitoes infected with the malariaparasite (疟原虫). However, the sweet-smelling substance is said to be harmless to
people and animals, Scientists at Hebrew University in Jerusalem developed the sugary bait by combining
fruit juice oils and boricacid (硼酸). The fruit juice oils get the attention of the mosquitoes, and the boric
acid kills the insects when they eat it.
The scientists took the sweet boric acid bait to the West African nation of Mali. Theysprayed (喷洒) it on the plants near the man-made ponds which are home to "Anopheles Gambiae", the mosquitoes that
carry the most deadly form ofmalaria (疟疾). The researchers also placed a sweet-smelling spray on the grasses near other ponds. Butitcontained no boric acid. Both of the substances also contained a
substance that would mark any mosquito that came in contact with the bait.In this way the scientists
could count the mosquitoes that fed on it. Yosef Schlein, an expert on the insects that affect human healh，led the sweet bait research. He says thirty-eight days of results show the sweet boric acid bait proved very effective in killing mosquitoes. At the ponds treated only with sweet-smelling bait, Professor Schlein says, more than seventy-five percent of mosquitoes fed on the false bait. He says most people do not know that female mosquitoes feed on sweet plant nectar to survive.
The Israeli researchers now hope to develop a bait that is even more desirable to the malaria
mosquitoes.
Boric acid is generally safe for human beings and other mammals. Professor Schlein says scientists
might be able to develop a mosquito bait for enclosed spaces. Boric acid has been used to kill other
insects, including cockroaches, termites and ants inside homes since the middle of last century.
1. Which of the following is TRUE about the sweet-smelling substance?
A. It is said to be harmless to people but harmful to animals.
B. It attracts the mosquitoes but fails to kill them most of the time.
C. It is actually created by Professor Schlein.
D. It is a mixture of fruit juice oils and boric acid.
2. What does the underlined word "it" in Paragraph 2 refer to?
A. A sweetsmelling spray.
B. The fruit juice oil.
C. A sweetsmelling spray with boric acid.
D. The sweet boric acid bait.
3. What do we know about Yosef Schlein?
A. He offered help to the researchers in the sweet bait research.
B. He is an expert on the substances that affect human health.
C. He thinks the sweet boric acid bait kills the malaria mosquitoes very effectively.
D. He thinks most people know female mosquitoes feed on sweet plant nectar to survive.
4. We can infer from the text that _____.
A. there will be fewer and fewer mosquitoes in Mali.
B. the new mosquito killer has been widely used in Africa.
C. malaria will become the most dangerous disease in the poorest areas of Africa.
D. the Israeli researchers want to develop a substance more attractive to the mosquitoes.

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