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题库 / Prep2007E2-CR-5
Microscopic plants called algae grow inside the top layer of sea ice in the Antarctic if enough sunlight reaches that layer of ice and enough seawater, which contains nutrients, reaches that layer after splashing onto the surface. Even though moderate snow cover reduces the sunlight that filters into the top layer, sea ice with moderate snow cover typically contains even more algae in the top layer than does sea ice with less snow cover.
Which of the following, if true, most helps to explain the apparent discrepancy?
As the weight of accumulated snow forces ice lower in the water, more seawater splashes onto the surface and seeps through the snow.
Seawater in the Antarctic often contains higher concentrations of nutrients than does seawater in more temperate regions.
As the air temperature around sea ice decreases during the winter, the likelihood decreases that snow will fall and thus add to any existing snow cover.
The nutrients on which algae rely are common in seawater throughout the Antarctic.
More sunlight filters through a layer of ice than through an equally thick layer of snow.
果因
∵Antarctic阳光直射、海水富含营养 ∴海冰表面生长藻
但雪堆积适中的地方藻长得比雪少的地方好，虽然雪会让阳光散掉
解释，寻找原因
A、因为雪的重量把冰面往下压，所以更多的水花飞溅起来洒在海冰表面（有营养）；提出他因，使矛盾化解
B、Antarctic的海水比其他地区富含营养；无关比较
C、气温降低，下雪、积雪可能性下降；无关
D、藻类赖以生长的营养在Antarctic很多；无关
E、冰层比同样厚度的雪层更会把光弄散；无关比较
光和营养----长的好
光没有，营养----长的好 解释
A 因为营养多了
B无关比较
C 这在说一个客观的事实
D 常见与否无关
E 无关比较
更多的雪把海冰壓低，使得更多富有營養的海水能夠滲透到冰的表層，讓海藻反而生長的更好。