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In September, in Britain, you may see a lot of birds (36) on roofs and telegraph wires. These birds are swallows. They are (37) together because, very soon, they will be flying (38) to much warmer lands, where they will find (39) small flying insects on which they (40) . There are no such insects (41) in Britain during the winter, as it is (42) cold for them. The swallows settle, fly off, swoop, and (43) again. This they do many times, for they are making short (44) flights in order to be fit for the long journey (45) them. (46) of these migrating birds leave Britain in the autumn. They fly (47) for hundreds of miles (48) they reach the warm lands of Africa. But not all the birds get there, for many of them perish in the stormy weather they meet with (49) . In the spring of the following year they (50) the long and tiring journey back to Britain. They return to the identical barn or tree in the (51) district which they had left the (52) autumn. How do these birds find their (53) there and back over such vast distances Nobody knows exactly (54) , but it has something to do (55) winds and air currents.
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Questions 81-90 are based on the following passage. It sounds like a science fiction, but researchers say it’s a scientific fact: Microscopic organisms dubbed "killer algae" are paralyzing fish with unknown toxins and then eating away at their flesh. They might be making people sick, too. The name given to this single-cell organism, or dinoflagellate, is Pfiesteria piscimorte- literally, "fish killer. " It was discovered at North Carolina State University in 1988, but at the same time, few scientists believed in its existence, much less in its highly unusual predatory nature. But ongoing research has led to international acknowledgment of the phenomenon and, recently, research funding. Seemingly prompted by an unknown substance secreted by fish, the aggressive creature swims into action. It sends neurotoxins into the water and air, paralyzing a fish’s nervous system, and causing it to gasp for air at the surface. Eventually the fish suffocates. The killer dinoflagellate then attaches itself to the fish and begins sucking away at its flesh. This macabre scenario may help solve several sea mysteries, such as why fishermen report seeing "fish walks" (fish trying to leave the water) and pools of dead fish with holes eaten through them. Whether humans are affected by the dinoflagellate’s toxin remains to be seen. Researchers think it’s unlikely eating fresh fish are in danger, but anyone with frequent exposure to the creature could be in peril. Several researchers working with the algae have reported bouts of memory loss and disorientation. To understand the killer algae further, scientists must fully characterize their toxin and determine what stimulates them to attack. They also need to know if the algae are hurting fish populations, and whether pollutants make them more likely to attack. It is implied in the passage that ______.
Why does Jane want to leave her present job
In September, in Britain, you may see a lot of birds (36) on roofs and telegraph wires. These birds are swallows. They are (37) together because, very soon, they will be flying (38) to much warmer lands, where they will find (39) small flying insects on which they (40) . There are no such insects (41) in Britain during the winter, as it is (42) cold for them. The swallows settle, fly off, swoop, and (43) again. This they do many times, for they are making short (44) flights in order to be fit for the long journey (45) them. (46) of these migrating birds leave Britain in the autumn. They fly (47) for hundreds of miles (48) they reach the warm lands of Africa. But not all the birds get there, for many of them perish in the stormy weather they meet with (49) . In the spring of the following year they (50) the long and tiring journey back to Britain. They return to the identical barn or tree in the (51) district which they had left the (52) autumn. How do these birds find their (53) there and back over such vast distances Nobody knows exactly (54) , but it has something to do (55) winds and air currents.
In September, in Britain, you may see a lot of birds (36) on roofs and telegraph wires. These birds are swallows. They are (37) together because, very soon, they will be flying (38) to much warmer lands, where they will find (39) small flying insects on which they (40) . There are no such insects (41) in Britain during the winter, as it is (42) cold for them. The swallows settle, fly off, swoop, and (43) again. This they do many times, for they are making short (44) flights in order to be fit for the long journey (45) them. (46) of these migrating birds leave Britain in the autumn. They fly (47) for hundreds of miles (48) they reach the warm lands of Africa. But not all the birds get there, for many of them perish in the stormy weather they meet with (49) . In the spring of the following year they (50) the long and tiring journey back to Britain. They return to the identical barn or tree in the (51) district which they had left the (52) autumn. How do these birds find their (53) there and back over such vast distances Nobody knows exactly (54) , but it has something to do (55) winds and air currents.
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