题干

以下有关变异的叙述,正确的是(  )

A:用普通二倍体西瓜培育出四倍体西瓜,再用普通二倍体西瓜给四倍体西瓜授粉,则四倍体植株上会结出三倍体无子西瓜

B:基因重组所产生的新基因型不一定会表达为新的表现型

C:基因重组导致杂合子Aa自交后代出现性状分离,产生新的基因

D:花药离体培养过程中,基因重组、基因突变和染色体变异均有可能发生

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B

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       I had four small children, their father died in an unknown disease. Money was always 1,but we had a roof over our heads,2on the table, clothes onour backs and, if not a lot, always enough.

        It was 3time and the big excitement for the kids was the 4of Christmas shopping at the mall.They talked and planned for weeks5time, asking each other andtheir grandparents 6they wanted for Christmas.I had saved $120 for presents to be shared by all five of us.

       The big day arrived and we started 7early. I gave 8of the four kids a twenty­-dollar bill and 9them tolook for gifts that cost about four dollars each.Then everyone 10.We had two hours to shop.

       Back in the car driving home, everyonewas in high Christmas spirits, laughing and teasing each other with hints and11about what they had bought. My younger daughter, Ginger, who was about eight years old, was 12quiet.I noted she had 13onesmall, flat bag with her. I could see enough 14the plastic bag to 15thatshe had bought candy bars—fifty-cent candy bars!Iwas so angry.What did you 16that twenty­-dollar bill I gave you?I wanted to17at her, but I didn't say anything 18we got home.I called her into my bedroom and closed the door, ready to be angry again when I asked her what she had done with the money.This is what she told me:

“I was looking 19,thinking of what to buy, and I stopped to read the little cards on one of the Salvation Army's‘Giving Trees.’One ofthe cards was for a little girl, four years old, and all she wanted for Christmas was a doll with clothes and a hair brush.20I took the card off the tree and bought the doll and the hairbrush for her and took it to the Salvation Army booth.”