更多" Scientists have discovered th"的相关试题:
[单项选择] Scientists have discovered that for the last 160,000 years, at least, there
has been a consistent relationship between the amount of carbon dioxide in the air
and the average temperature of the planet. The importance of carbon dioxide in
regulating the Earth’s temperature was confirmed by scientists working in eastern
(5) Antarctica. Drilling down into a glacier, they extracted a mile-long cylinder of ice
from the hole. The glacier had formed as layer upon layer of snow accumulated year
after year. Thus drilling into the ice was tantamount to drilling back through time.
The deepest sections of the core are composed of water that fell as snow 160,000 years
ago. Scientists in Grenoble, France, fractured portions of the core and
temperature and of atmospheric
(10)measured the composition of ancient air released from bubbles in the ice. Instruments
were used to measure the ratio of certain isotopes in the frozen water to get an idea
of the p
A. Chemical causes of ice ages
B. Techniques for studying ancient layers of ice in glaciers
C. Evidence of a relationship between levels of carbon dioxide and global temperature
D. Effects of plant life on carbon dioxide levels in the atmosphere
[填空题] Scientists have discovered that plants themselves produce many poisonous chemicals for (36) ________ against insects. But insects have developed ways of (37) ________ with them and, in fact, have been eating plants for about 250 million years. Now insects are using these same (38) ________ to deal with man-made poisons—insecticides. This is why (39) ________ of insects to insecticides has developed so (40) ________.
What should be done Scientists studying the problem suggest that farmers use less insecticides. At the moment, farmers (41) ________ spray crops as a (42) ________ against problems that are caused by large numbers of pests. They should, instead, spray only where pests have actually been seen. Secondly, farmers could use a (43) ________ of two or three insecticides at once. (44) __________________________.
The most surprising suggestion, perhaps, is that at certain times of the year, (45) ___________________________. The new insects will mate with those which
