問題詳情


(B) When the Arctic Ocean freezes over in the autumn, polar bears set off in search of their favorite meals: fatty ringed sealsand bearded seals. By the summer, the sea ice begins to melt and break apart. (21) tasty seals, polar bears spend the summerfasting. As the planet warms, the warmer ice-free season is getting longer and longer. So what’s a hungry bear to do? Scientistsonce thought that polar bears might survive by supplementing their pinniped diet by turning to terrestrial foods. “And we’veknown for a long time, going back to research in the early 70s, even going back to early explorer logs, (22) polar bears willconsume terrestrial based foods. But the debate was always whether those foods actually add up, energetically.”  To find out whether these substitutes provide enough nutrition to make up for the lost seals, Pilfold and his colleagues did astudy in which they estimated the weight lost each day by polar bears in the wilds of western Hudson Bay during the ice-freeseason, when they could (23) be chowing down on terrestrial foods. Then they compared that to the weight lost by bearsthat are temporarily held in Manitoba’s Polar Bear Alert Program. While captive, the bears do not eat. They drop about onekilogram each day. But the wild bears, who had access to the Arctic snack bar, lost the same amount of weight each day, whichis really saying that the terrestrial foods do not have dense enough energy to offset the mass loss. As a result, this idea that bearscan just switch from eating sea ice-based food to land food simply does not (24) .  The problem is that polar bears evolved to rely on the marine diet. “The food on land is protein and carbohydrate based, andthe food the polar bears really focus on is fat. Fat is (25) for these bears; they’re highly adapted to absorbing that fat intotheir system and putting it onto their body as body mass, so they can fast on it later on. And the only thing that’s going to providethem with that type of fat are marine mammals. And they can only access those marine mammals when there’s sea ice.”
21.
(A) Because lacking
(B) Due to a dearth of
(C) Having a slew of
(D) Deprived access to

參考答案

答案：B
難度：適中0.586207
統計：A(4),B(17),C(4),D(3),E(0)

內容推薦

內容推薦