Polarbearsaresufferingina  61  (warm)worldthaneverbefor...

问题详情：

Polar bears are suffering in a   61   (warm) world than ever before.

Polar bears live in environments too cold for most animals.   62      much of the year, they live and hunt on the frozen Arctic sea ice. Nature has prepared   63     for the cold conditions. But nothing has prepared the bears for the danger that   64     (threat) the only home they know.

The polar bears’ world is melting. Studies show that the polar ice has reduced by 9.8% every 10 years   65     1978. Now about 20,000 to 25,000 polar bears live in the Arctic. Polar bears depend on the sea ice for their   66     (survive). “The sea ice is more than just this platform that the bears walk over,” says Andrew Derocher,   67     scientist who studies North American polar bear populations. “    68    it, they can’t exist.”

Some melting and refreezing of the polar ice is natural.     69     in a warmer world, these cycles speed up, and bears have less time to hunt. Normally, they have three months in the spring when they gain more weight. The extra fat is used later,      70    the bears are not actively hunting.

【回答】

61. warmer   句中出现than，要用比较级。

62. During  during much of the year 在一年的大多数时候

63. them   讲的是Polar bears ，这里需要用宾格them。

64. threatens  that引导的定语从句，缺少谓语，要用threat的动词threaten, 主语是danger，要用threatens。 

65. since   since+点时间，用现在完成时。

66. survival  their修饰名词。

67. a  单数名词前，表泛指，用a。

68. Without 没有*，他们无法生存。

69. But   一些极地*的融化和重新冻结是很自然的，但是在一个更暖和的世界,这些周期加快了。

70. when当熊不积极打猎时，这些额外的脂肪就会被用掉。

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