题干

如图为某种植物幼苗(大小、长势相同)均分为甲、乙两组后,在两种不同浓度的KNO3溶液中培养时鲜重的变化情况(其他条件相同且不变),下列有关叙述,正确的是(  )

A:6h时,甲组幼苗因根系开始吸收K+、NO3﹣,吸水能力增强,使鲜重逐渐提高

B:由于根细胞失水,3h时,甲组植物细胞细胞液的浓度大于外界溶液浓度

C:12h后,若继续培养,甲组幼苗的鲜重可能超过处理前,乙组幼苗将死亡

D:该实验若把KNO3溶液改为蔗糖溶液,结果相同

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答案(点此获取答案解析)

C

同类题5

阅读理解。

阅读下列短文,从每题所给的四个选项 (A 、B 、C  和 D )中,选出最佳选项。

    My friend Jennie Crossen gave her bone marrow (骨髓) to a 51-year-old woman with leukemia, a woman she has never met.

    At the end of March, the Red Cross called back. Six different blood elements were tested; Jennie matched five completely and was about a 3/4 match of the sixth. So she was the best match.

    In April, Jennie went for a complete physical exam by one of the doctors who would perform the surgery. The doctor had to make sure that it would be no threat to her. The doctor told her that the surgery would entail having two quarts of bone marrow extracted from her hip bones. Jennie would probably be released the same day the surgery took place and should expect to be sore for a couple of months.

    "I didn't think it was that big a deal until I realized I was a match," Jennie said, "There wasn't a question in my head. It didn't seem like something that was going above and beyond."

    Jennie was left with two very small scars on her lower back from the surgery and was given medication to help dull the pain. She still felt a great deal of pressure on her lower back. "Being only 21, I feel like I am not old enough to significantly impact someone's life," Jennie said, "It seems strange to me that I could possibly save this woman's life which was being cut short by cancer."

    Three weeks after the surgery, Jennie received a call from the Red Cross representative who told her the transplant was successful. "I feel good, and I think it will actually work for her," she said, "So many people say they'd only donate if it was for a family member or close friend. This woman is someone's family and someone's friend. Obviously, no one she knows is a match, and the fact that you'd be able to help a perfect stranger is great."