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  3. A certain species of desert lizard digs tunnels in which to lay its eggs. The eggs must incubate inside the tunnel for several w

A certain species of desert lizard digs tunnels in which to lay its eggs. The eggs must incubate inside the tunnel for several w

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问题 A certain species of desert lizard digs tunnels in which to lay its eggs. The eggs must incubate inside the tunnel for several weeks before hatching, and they fail to hatch if they are disturbed at any time during this incubation period. Yet these lizards guard their tunnels for only a few days after laying their eggs.
Which of the following, if true, most helps explain why there is no need for lizards to guard their tunnels for more than a few days?
选项 A、The eggs are at risk of being disturbed only during the brief egg-laying season when many lizards are digging in a relatively small area.
B、The length of the incubation period varies somewhat from one tunnel to another.
C、Each female lizard lays from 15 to 20 eggs, only about 10 of which hatch even if the eggs are not disturbed at any time during the incubation period.
D、The temperature and humidity within the tunnels will not be suitable for the incubating eggs unless the tunnels are plugged with sand immediately after the eggs are laid.
E、The only way to disturb the eggs of this lizard species is by opening up one of the tunnels in which they are laid.
答案A
解析 Argument Construction
Situation Lizards of a certain species dig tunnels in which they lay their eggs. Although the eggs fail to hatch if disturbed during their several weeks of incubation, the lizards guard the tunnels for only a few days after laying the eggs.
Reasoning What would help to explain why the lizards have to guard their tunnels for only a few days? For the lizards to survive as a species, their behaviors must ensure that enough of their eggs hatch. Thus, they must successfully prevent enough of their eggs from being disturbed in the tunnels throughout the several weeks of incubation. If guarding the tunnels for only a few days accomplishes this, then some other factor must prevent the eggs from being disturbed during the remaining weeks. Evidence of any such factor would help to explain why the lizards do not have to guard the tunnels longer. For example, to protect the eggs without guarding them, the lizards might conceal the tunnel entrances after the first few days. Or animals likely to disturb the eggs might only be present for those first days, in which case there would be nothing for the lizards to guard against thereafter.
A Correct. This suggests that the only creatures likely to disturb the eggs are other lizards of the same species digging tunnels to lay their own eggs at around the same time. If so, each lizard can safely leave its eggs unguarded after a few days because all the other lizards will have finished digging.
B Even if the incubation period varies somewhat, the passage says it always lasts several weeks. So this does not explain why the lizards have to guard the tunnels for only a few days.
C If many eggs fail to hatch even when undisturbed, that is all the more reason for the lizards to protect the remaining eggs from disturbance throughout the incubation period so that at least some will hatch. So it does not explain why the lizards guard their tunnels only for a few days.
D Whether or not immediately plugging the tunnels with sand is enough to protect the eggs, this behavior does not explain why the lizards subsequently guard the tunnels for a few days and then leave for the rest of the incubation period.
E Even if it is impossible to disturb the eggs without opening the tunnels, that does not explain why the lizards guard the tunnels for a few days and then leave for the rest of the incubation period.
The correct answer is A.
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