Malaria is worlds second most common disease causing over【C1】______infections and one mill

Malaria is worlds second most common disease causing over【C1】______infections and one million deaths every year.【C2】______it is one of those diseases which is beginning to increase as it develops resistance【C3】______treatments. Even in the UK, where malaria has been effectively【C4】______more than 2,000 people are infected as they return from trips abroad and the numbers are rising. 【C5】______the fact that malaria has been around for so long, surprisingly【C6】______is known about how to【C7】______or prevent it. Mosquitoes,【C8】______are the carriers of the disease, are attracted to heat, moisture and carbon dioxide but how they sought【C9】______this mixture to repeatedly select one individual for attention over【C10】______is not understood. The fight against malaria often seems to focus on the work of medical researchers. But【C11】______is low because malaria is a third world condition and【C12】______troubles the rich, industrialized countries.【C13】______malaria is a disease of【C14】______The richer countries have managed to eradicate malaria by extending agriculture and having proper drainage【C15】______mosquitoes cannot breed. In China, making use of【C16】______impregnated netting around beds reduced infection【C17】______from over 1 million per year to around 65,000. But the search for medical cures goes on. Some researchers still have high hopes for DNA【C18】______vaccines which worked well in trials【C19】______mice. Others are not so confident and expect a wait of【C20】______another 15 years before any significant development.

【C1】

A．500 million

B．500 millions

C．500 million of

D．500 millions of

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