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问题 单项选择题

（）已广泛用于地铁、铁路、公路、市政、水电等隧道工程。

A.盾构掘进机

B.顶管机

C.高空作业车

D.挖掘机

答案

参考答案：A

单项选择题

E


Dick was born in a poor family. His father had a small boat and went fishing in the morning and sold the fish in the market in the afternoon. Then he bought some food for his family. When winter came, they were often hungry. One morning the hungry man fell into the river and wasn’t found. Dick’s mother left her three-year-old son without saying good-bye. His aunt had to look after him.
Twenty years passed. Dick became a tall, p man. He found work on a farm. lie worked hard and wanted to get more money. He often went to see his aunt with some nice presents. The woman was very happy but one day she died in a traffic accident. The young man was very sad. After he buried her, he decided to buy a beautiful tombstone(墓碑) for her. He went to town and came in a shop, but all the tombstones were too expensive. He asked, "Do you sell an old tombstone, sir "Yes, we do, sir," answered the shopkeeper. "Is it as expensive as the new one"
"No, it’s much cheaper," said the man. "But another name was engraved (刻) on it. " "It doesn’t matter, " said Dick. "My aunt couldn’t read. \

If ______ , the family members were hungry.

A．Dick’s father could catch no fish in winter

B．Dick’s father had a boat in winter

C．Dick’s father had to look after him in winter

D．no food was sold in winter
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问答题

A．条件(1)充分，但条件(2)不充分。

B．条件(2)充分，但条件(1)不充分。

C．条件(1)和(2)单独都不充分，但条件(1)和条件(2)联合起来充分。

D．条件(1)充分，条件(2)也充分。

E．条件(1)和(2)单独都不充分，条件(1)和条件(2)联合起来也不充分。

a3+a5=5．
(1){an}是等比数列；
(2)a2a4+2a3a5+a4a6=25．
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