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2015年9月13日托福阅读真题预测：
PASSAGE 1
Aviculturists, people who raise birds for commercial sale, have not yet learned how tosimulate the natural incubation of parrot eggs in the wild. They continue to look for betterways to increase egg production and to improve chick survival rates.
When parrots incubate their eggs in the wild, the temperature and humidity of the nestare controlled naturally. Heat is transferred from the bird's skin to the top portion of theeggshell, leaving the sides and bottom of the egg at a cooler temperature. This temperaturegradient may be vital to successful hatching. Nest construction can contribute to this temperature gradient. Nests of loosely arranged sticks, rocks, or dirt are cooler in temperatureat the bottom where the egg contacts the nesting material. Such nests also act as humidityregulators by allowing rain to drain into the bottom sections of the nest so that the eggs arenot in direct contact with the water. As the water that collects in the bottom of the nest evaporates, the water vapor rises and is heated by the incubating bird, which adds significanthumidity to the incubation environment.
In artificial incubation programs, aviculturists remove eggs from the nests of parrots andincubate them under laboratory conditions. Most commercial incubators heat the eggs fairlyevenly from top to bottom, thus ignoring the bird's method of natural incubation, and perhapsreducing the viability and survivability of the hatching chicks. When incubators are notused,aviculturists sometimes suspend wooden boxes outdoors to use as nests in which to place eggs. In areas where weather can become cold after eggs are laid, it is very important tomaintain a deep foundation of nesting material to act as insulator against the cold bottom ofthe box. If eggs rest against the wooden bottom in extremely cold weather conditions, theycan become chilled to a point where the embryo can no longer survive. Similarly, these boxesshould be protected from direct sunlight to avoid high temperatures that are also fatal to thegrowing embryo. Nesting material should be added in sufficient amounts to avoid both extreme temperature situations mentioned above and assure that the eggs have a soft, secureplace to rest.
1. What is the main idea of the passage ?
(A) Nesting material varies according to the parrots' environment.
(B) Humidity is an important factor in incubating parrots' eggs.
(C) Aviculturists have constructed the ideal nest box for parrots.
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