题干

下面有关生物实验的叙述中错误的有( )
①西瓜汁中含有丰富的葡萄糖和果糖,是还原糖鉴定实验的理想材料
②用显微镜观察根尖细胞有丝分裂时,看到的分生区细胞在右下方,为使观察目标移至视野中央,应该将装片向右下方移动
③将肝脏研磨液煮沸冷却后,加入过氧化氢溶液中立即出现大量气泡
④观察洋葱很尖细胞有丝分裂时,可用高倍镜看到细胞从分裂前期到中期的变化
⑤观察细胞质壁分离时,浸润在0.3g/ml蔗糖溶液中的洋葱表皮细胞液泡颜色变深
⑥实验材料的数量、温度和时间都可能是实验的变量
⑦各种实验都必须设置空白对照实验,确保单一变量

A:①③④⑦

B:①②③④

C:③④⑤⑥

D:②③④⑤

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答案(点此获取答案解析)

A

同类题2

    It snowed again. My seventh Christmas was round the corner. I dreamed of getting the present from Father Christmas until my elder sister dropped the bomb, “There is no Father Christmas.”
I ran to my grandmother’s house, for she always told the truth. Grandma was at home. I told 1 everything. "No Father Christmas?" she was a little 2. “Don't believe it. Put on your coat, and let's go.”
   “Go? Where, Grandma?” I asked.
   “Kerby's Store.”
    As we walked through its doors, Grandma handed me ten dollars and said, "Take the 3 and buy something for someone who needs it. I'll wait for in the car.”Then she turned and walked out of the Kerby's.
    For a few seconds I just stood there, holding the money, wondering 4 to buy, and who to buy it for.
    I thought of 5 I knew: my family, my friends, my neighbors … I suddenly thought of Bobbie Decker, a 6 with bad and messy hair. He sat right behind me 7 Mrs. Pollack's class.
    Bobbie 8 went to any party during the winter. His mother always wrote a note, telling the teacher that he had a cough, 9 we all knew that he didn't have a cough, and he didn't have a coat. I decided to buy Bobbie a red warm coat 10 he would like.
    That evening, Grandma helped me wrap the coat in Christmas paper and ribbons, and 11 “To Bobbie, From Father Christmas” on it. Grandma told me Father Christmas never let people know that he 12 them. Then she drove me over to Bobbie's house, telling that I was helping Father Christmas 13 the presents.
    Grandma parked the car along the street, and we hid behind the trees near Bobbie's house. Then Grandma said to me, “All right, Father Christmas, get going.”
    I took a deep breath, rushed to his front door, put the present down. 14 the door, rang the doorbell and flew back to the safety of the 15 and Grandma. We waited breathlessly in the dark for the front door to open. Finally it did, and there stood Bobbie.
That night, I realized that Father Christmas was alive and well, and we were on his team.