[单项选择] Spring is usually prime food time for some 1,200 polar bears along Canada’’s Hudson Bay. Each year they plunder the bay’’s ice floes, smash open the snow caves of seals, and stuff themselves on seal pups. But in recent years the bears’’ feast has turned into slimmer pickings. Why Temperatures at Hudson Bay have risen by one half degree Fahrenheit every decade since 1950. Winter ice on the bay melts three weeks earlier than it did just 25 years ago, which means three fewer weeks of polar bear mealtime. Result: Polar bears are 10 percent thinner and produce 10 percent fewer cubs than they did 20 years ago. And though climatologists hotly debate the causes behind Earth’’s Arctic meltdown, "these changes are startling and unexpected, " says James McCarthy, co-leader of the United Nations Intergovernmental Panel on Climate Change. The plight of polar bears is just the tip to the iceberg when it comes to mounting evidence of global warming. "There’’s definitely a stark contrast w
A. Water shortages in cities.
B. Earlier thawing of lakes and rivers.
C. Increased levels of greenhouse gases.
D. The rapid extinction of the polar bear.

[单项选择] Spring is usually prime food time for some 1,200 polar bears along Canada’’s Hudson Bay. Each year they plunder the bay’’s ice floes, smash open the snow caves of seals, and stuff themselves on seal pups. But in recent years the bears’’ feast has turned into slimmer pickings. Why Temperatures at Hudson Bay have risen by one half degree Fahrenheit every decade since 1950. Winter ice on the bay melts three weeks earlier than it did just 25 years ago, which means three fewer weeks of polar bear mealtime. Result: Polar bears are 10 percent thinner and produce 10 percent fewer cubs than they did 20 years ago. And though climatologists hotly debate the causes behind Earth’’s Arctic meltdown, "these changes are startling and unexpected, " says James McCarthy, co-leader of the United Nations Intergovernmental Panel on Climate Change. The plight of polar bears is just the tip to the iceberg when it comes to mounting evidence of global warming. "There’’s definitely a stark contrast w
A. spring is usually a good time for polar bears to carry out their mating rituals
B. the polar bears usually eat a lot in the spring
C. spring is generally a good time to hunt polar bears
D. polar bears usually hibernate in the spring

[单项选择]　　 If food is allowed to stand for some time, it putrefies .When the putrefied material 　　is examined microscopically ,it is found to be teeming with bacteria. Where do these 　　bacteria come from, since they are not seen in fresh food Even until the mid-nineteenth 　　century, many people believed that such microorganisms originated by spontaneous (5) generation ,a hypothetical process by which living organisms develop from nonliving matter. 　　The most powerful opponent of the theory of spontaneous generation was the French chemist 　　and microbiologist Louis Pasteur(1822-1895).Pasteur showed that structures 　　present in air closely resemble the microorganisms seen in putrefying materials .He did (10)this by passing air through guncotton filters, the fibers of which stop solid particles. After 　　the guncotton was dissolved in a mixture of alcohol and ether, the particles that it had 　　trapped fell to the bottom of the liquid and were examined on a microscope slide .Pasteur
A. Pasteur’’s influence on the development of the microscope.
B. The origin of the theory of spontaneous generation.
C. The effects of pasteurization on food.
D. Pasteur’’s argument against the theory of spontaneous generation.

[填空题]make some food to eat