The sound of a mosquito can mean trouble in many parts of the world. The bite of the mosquito can be deadly. The insects carry serious diseases like malaria. The World Health Organization estimates that almost 630,000 people died from malaria and malaria-related causes in 2012, most of these cases were in African countries south of the Saharan desert.
In the United States, scientists are seeking new ways to fight malaria. A group of California scientists is working to develop a more effective and less costly substances to protect people from mosquito.
The researchers work at the University of California Riverside. They are investigating the sense of smell in mosquitoes. They found the insects use the same receptor for identifying carbon dioxide in human breath as they do for the smell of our skin.
Anandasankar Ray is leading the investigation. He says scientists tested more than a million chemical compounds until they found a substance called Ethyl pyruvate. He says Ethyl pyruvate makes the mosquitoes' receptor inactive.
"When we apply Ethyl pyruvate to a human arm and offer it to hungry mosquitoes in a cage, then very few of the mosquitoes are attracted to the human arm because only a few of them are able to smell it out," said Ray.
Genevieve Tauxe is a member of the UC Riverside research team. She says it was not easy to find the neurons of noble cells that recognise both the smell of human breath and skin. She describes a device the researchers are using to examine mosquitoes.
"With this apparatus, we are able to insert a very small electrode into the part of the mosquito's nose, effectively, where its olfactory neurons are and where the smell is happening," said Tauxe.
The scientists use these instruments to look for the signals that a mosquito's neurons send to its brain when it finds an interesting smell. Computer screen images show when the sense is strong or weak.
Anandasankar Ray says a product based on Ethyl pyruvate may cost less to manufacture than DEET, the most effective chemical treatment now in use. He says DEET is too costly for most people who live in areas affected by malaria.
"Perhaps by finding odors that can attack other target receptors, we will be able to improve upon DEET and finally have the next generation of insect behavior control products," said Ray.
The scientists believe they will soon be able to find a way to manufacture less costly and more effective products for the fight against mosquitoes.420
According to the passage，scientists found a substance called_________.

A．DEET

B．Ethyl pyruvate

C．carbon dioxide

D．target receptors

From the passage, we know that__________.

A．DEET is the most effective chemical treatment in use and it is not expensive.

B．scientists have not made products that are less costly and more effective to fight against mosquitoes.

C．new products will be more effective than DEET but will be costly.

D．DEET is not effective but expensive.

What is the main idea of the passage？

A．scientits help people to prevent from malaria.

B．scientits find how mosquitoes carry diseases.

C．scientits work hard to make new products to avoid the malaria.

D．scientits find new substances to fight mosquitoes.

Where does this text probably come from ?

A．Children’s literature	B．Science fiction
C．An advertisement	D．A health report

According to the passage，which of the following statements is correct？

A．Ethyl pyruvate does not make the mosquitoes' receptor inactive.

B．When we apply Ethyl pyruvate to a human arm，most of the mosquitoes are not attracted to the human arm.

C．Now we have not effective products to prevent from the mosquitoes.

D．Almost 630,000 people died from malaria and malaria-related causes in 2012, all the cases were in African countries.