题干

=干细胞的研究是21世纪最重要的研究领域,治疗白血病经常用干骨髓中的造血干细胞来产生不同种类的细胞,根本原因是这些造血干细胞(    )

A:具有旺盛的分裂能力的细胞

B:高度分化的细胞

C:能合成不同种类细胞需要的蛋白质

D:具有与受精卵相同的全套遗传基因

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答案(点此获取答案解析)

D

同类题4

   Short and shy, Ben Saunders was the last kid in his class picked for any sports team. "Football, tennis Cricket — anything with a round ball, I was useless." he says now with a laugh. But back then he was the object of jokes in school gym classes in England’s rural Devonshire.
It was a mountain bike he received for his 15th birthday that changed him. At first the teen went biking alone in a nearby forest. Then he began to cycle along with a runner friend. Gradually, Saunders set his mind building up his body, increasing his speed, strength and endurance. At age 18, he ran his first marathon.
   The following year, he met John Ridgway, who became famous in the 1960s for rowing an open boat across the Atlantic Ocean. Saunders was hired as an instructor at Ridgway’s school of Adventure in Scotland, where he learned about the older man’s cold-water exploits (成就). Intrigued, Saunders read all he could about Arctic explorers and North Pole expeditions, then decided that this would be his future. Journeys to the Pole aren’t the usual holidays for British country boys, and many people dismissed his dream as fantasy. "John Ridgway was one of the few who didn’t say, ’You are completely crazy,’" Saunders says.
   In 2001, after becoming a skilled skier, Saunders started his first long-distance expedition toward the North Pole. He suffered frostbite, had a closer encounter (遭遇) with a polar bear and pushed his body to the limit.
   Saunders has since become the youngest person to ski alone to the North Pole, and he’s skied more of the Arctic by himself than any other Briton. His old playmates would not believe the transformation.
   This October, Saunders, 27, heads south to explore from the coast of Antarctica to the South Pole and back, an 1800-mile journey that has never been completed on skis.