已知线段AB，延长AB到C，使BC=2AB，又延长BA到D，使DA=12AB，那_爱下问搜题

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问题选择题

已知线段AB，延长AB到C，使BC=2AB，又延长BA到D，使DA=

1

2

AB，那么（　　）

A．BD=

3

4

BC

B．DC=

5

2

AB

C．DA=

1

2

BC

D．BD=

4

3

AB

答案

由题意画图为：

∵BC=2AB，DA=

1

2

AB；

∴BD=AB+

1

2

AB=

3

2

AB=

3

2

×

BC

2

=

3

4

BC，故A正确；

∴DC=DA+AB+BC=

1

2

AB+AB+2AB=

7

2

AB，故B错误；

∴DA=

1

2

AB=

1

2

×

BC

2

=

1

4

BC，故C错误；

∴BD=DA+AB=

1

2

AB+AB=

3

2

AB，故D错误；

故选A．

完形填空

Mr. and Mrs. Green were very worried about their son, Leo. He seemed to be dumb( 哑的）      he was normal（正常） in every other way. Mr. and Mrs. Green tried to get him to     ,but with no success. When Leo was six years old, the best doctors in town      him carefully, but could find nothing wrong.
And he seemed to be smart（聪明）. It was just that he _     spoke.
“There might be something wrong with his   ,and he doesn’t know he’s able to speak,” one doctor said. “But he can read and write ,” said Mr,Green. “We’ve written him notes,telling him that he can speak.” “It’s really very    ,” another doctor said.Perhaps he’ll be able to speak some day,”    passed. Leo went to university.But he did not say   word Then one day,Leo was having a meal with his parents.He looked up from his   and said, “pass me the salt, please.”
Mr. and Mrs. Green were excited. “You spoke! You spoke!” they cried. “ Why have you       so long to speak?” “I didn’t have anything to say，he said. “Until now everything was good. But you forgot to put salt in potatoes. ”

C．examined（检查）

D．mind（思想）

问答题简答题

列出肾上腺各主要腺细胞的名称及其分泌的激素。