题干

下列有关生物变异的说法中正确的是     ()

A:即使遗传物质不发生改变,生物也可能出现变异性状

B:在细胞分裂过程中,如果染色体数目发生了变化,则说明发生了染色体变异

C:在减数分裂过程中,如果同源染色体之间发生了交叉互换,则必然发生基因重组

D:如果某果蝇的长翅基因缺失,则说明其发生了基因突变

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A

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阅读理解

C

    Fat and shy, Ben Saunders was the last kid in his class picked for any sports team. “Foothall, tennis, cricket-anything with a round ball, I was useless,” he says now with a laugh. But back then he was the one always made fun of in school gym classes in Devonshire, England.

    It was a mountain bike he received for his 15th birthday that changed him. At first he went biking alone in a nearby forest. Then he began to-ride the bike along with a runner friend. Gradually, Saunders set up his mind on building up his body, increasing his speed and strength. At the age of 18, he ran his first marathon.

    The following year he met John Ridgway and was hired as an instructor at Ridgway's school of adventure in Scotland, where he learnt about Ridgway's cold-water exploits. Greatly interested, Saunders read all he could about North Pole explorers and adventures, then decided that this would be his future.

    In 2001, after becoming a skillful skier, Saunders started his first long-distance expedition towards the North Pole. It took unbelievable energy. He suffered frostbite, ran into a polar bear and pushed his body to the limit, pulling his supply-loaded sled(雪橇)up and over rocky ice.

    Saunders has since become the youngest person to ski alone to the North Pole, and he's skied more of the North Pole by himself than any other British man. His old playmates would not believe the change.

    Next October, Saunder, 27, heads south from the coast of Antarctica to the South Pole and back, a 2900-kilometer journey that has never been completed on skis.