It may be hard to believe that some experts consider tiny mosquitoes to be the most dangerous creatures in the world. However, categorizing these insects _(1)_ dangerous animals makes good sense, considering the fact that mosquito-borne illnesses kill millions of people each year. The list of deadly diseases includes malaria, encephalitis, West Nile virus, yellow fever, and dengue fever. In addition to infecting humans with life-threatening illnesses, mosquitoes also _(2)_ diseases to animals through parasites and viruses. _(3)_ only a few of the 3,500 species of mosquitoes are capable of passing on diseases, the blood-sucking nature of these pests makes them universallyhated. Tens of millions of years of evolution have turned mosquitoes into adepthunters with a _(4)_ sense of survival. One way that mosquitoes have evolved totrack down potential meals of blood is through sensing carbon dioxide and lactic acid, which are substances emitted by mammals and birds, from a range of up to 36 meters. These insects can also detect heat and use visual _(5)_ to findhosts to feed on. _(6)_ visible clues, mosquitoes are drawn to movement and people wearing clothing that is in contrast to their surroundings. For those wondering why some mosquitoes risk _(7)_ blood from hosts who would gladly kill them, the reason is that the protein found in blood acts asnourishment for producing eggs. In fact, only female mosquitoes suck blood. Males seek out nectar and other sugars to consume.
1. (A) for (B) to (C) as (D) in 2. (A) transmit (B) recruit (C) surpass (D) intervene 3. (A) When (B) While (C) Unless (D) Until 4. (A) profitable (B) parallel (C) logical (D) keen 5. (A) restraints (B) sensations (C) thresholds (D) sanctions 6. (A) On the verge of (B) In terms of (C) In place of (D) For fear of 7. (A) to be drunk (B) drink (C) drinking (D) to drink
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