把细胞中染色体、DNA和细胞核按照从大到小的顺序排列，正确的是（ ）
A．染色体-细胞核-DNA
B．细胞核-染色体-DNA
C．染色体-DNA-细胞核
D．细胞核-DNA-染色体
细胞核是遗传信息库，是细胞的控制中心；细胞核中能被碱性染料染成深色的物质叫做染色体，它是由DNA和蛋白质两种物质组成，DNA是主要的遗传物质，它的结构像一个螺旋形的梯子．一条染色体上包含一个DNA分子．一个DNA分子上包含有多个基因，基因是染色体上具有控制生物性状的DNA片段．因此，从“大到小”的顺序排列依次是：细胞核-染色体-DNA．可见B符合题意．
故选：B
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| This is my third story. When I was 17, I read a quote that 1 something like, "If you live each day 2 it was your last, someday you'll most certainly be right." Since then, for the past thirty-three years, I've looked 3 the mirror every morning and asked myself. "If today were the last day of my life, would I want to do what I am about to do today?" And whenever the answer has been "No" for too many days in a 4 , I know I need to change something. About a year ago I was 5 with cancer. Tile doctors told me this was almost certainly a type of cancer that is incurable, and that I should 6 to live no longer than three to six months. They advised me to go home and get my 7 in order, which is doctors' code for "prepare to 8 ". Later that evening when the doctors 9 the cells taken from my pancreas (胰腺) under a microscope, they started crying because it turned out to be a very rare form of pancreatic cancer that is 10 with surgery. I had the surgery and, 11 , I'm fine now. This was the closest I've been to facing death, and I hope it's the closest I get for a few more decades. Death is the 12 we all share. No one has 13 escaped it. And that is 14 it should be, because Death is very likely the single 15 invention of life. It's Life's change agent. It clears out the old to make 16 for the new. Your time is 17 , so don't waste it living someone else's life. Don't be trapped by dogma (信条)-which is living with the results of other people's thinking. Don't let the noise of 18 opinions drown out your own inner voice. And most importantly, have the courage to 19 your heart and intuition (直觉). They 20 already know what you truly want to become. Everything else is secondary. | ||||
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