题干

某同学从生物学资料中得知:“植株上的幼叶能合成生长素,防止叶柄脱落”.为了验证这一结论,该同学利用如图所示的植株进行实验,实验中所需要的步骤是

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①选取同种生长状况相同的植株3株,分别编号为甲株、乙株、丙株

②将3株全部去掉顶芽

③将3株全部保留顶芽

④将甲、乙两株去掉叶片,保留叶柄,并在甲株的叶柄横断面   涂上一定浓度的生长素,丙株保留幼叶

⑤将去掉叶片的甲、乙两株叶柄横断面均涂上一定浓度的生长素

⑥观察3株植株叶柄脱落情况.

A:①③④⑥

B:①②④⑥

C:①③⑤⑥

D:①②⑤⑥

上一题 下一题 0.0难度 选择题 更新时间:2014-08-27 05:54:46

答案(点此获取答案解析)

B

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    Last month some thieves stole a valuable teapot from a museum in Hong Kong. They took the teapot to America, but the American police found it. The museum sent Mr. Chan, a member of the museum staff, to collect the teapot. On the plane back to Hong Kong, he noticed two men. They were watching him closely. "Perhaps they're going to steal the teapot again. I must think of a plan,” he thought.

    Mr Chan's daughter, Amy, met him at Hong Kong Afimor. Mr Chan NS was carrying two boxes. He gave his daughter the pink box and said to her in a low voice, "Take this gift box home with great care." He walked away with the brown one. The two men followed him.

    Amy opened the box at home. She was expecting a pair of sports shoes, but she just found an old teapot. "This is not a very interesting gift," said Amy, a bit disappointed." That's all right. Let's make some tea in it," said her mother. Then they found a note in the teapot. It said, "Dear Amy, __ Love Dad.”

    The two men kidnapped(绑架)Mr. Chan on his way to the museum. They opened his box and found a pair of sports shoes inside."Wheres the teapot?” the two thieves shouted at the top of their voice with red faces." How dare you cheat us? We saw you give your daughter a box at the airport. Come with us! We're going to search your home, one of them said。

    When the thieves entered Mr. Chan's flat, it was dark and quiet. All of a sudden, the door closed and the lights went on. The police were waiting inside.

    Amy and her mother came out of the bedroom with the teapot. "That teapot is very valuable, said Mr. Chan. "A long time ago it belonged to an emperor. He drank tea from it."

    “We were going to drink tea from it, too, "said Amy, laughing.