关于放射性元素的半衰期[ ] A.是原子核质量减少一半所需的时间 B.是原子核有

题型:不定项选择

问题:

关于放射性元素的半衰期[ ]

A.是原子核质量减少一半所需的时间

B.是原子核有半数发生衰变所需的时间

C.与外界压强和温度有关,与原子的化学状态无关

D.可以用于测定地质年代、生物年代等

考点:半衰期
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瑞氏染料是一种复合染料,组成是()

A.酸性伊红和碱性亚甲蓝

B.碱性品红和碱性亚甲蓝

C.甲基红和亚甲蓝

D.伊红和糊精

E.伊红和酸性亚甲蓝

题型:不定项选择

先天性心脏病室间隔缺损的手术入路包括()

A.左心室

B.右心室

C.左心房

D.右心房

E.肺动脉

题型:不定项选择

Mr. Knight was the manager of a hotel. One weekend all of the hotels in the city were full because there was a large meeting. On Friday, three men came into the hotel and asked for rooms. Mr. Knight said there were no rooms ready because of the meeting. The men were unhappy.

Mr. Knight wanted to help them. He remembered that Room 418, a small room, was empty. He asked them if they could share a room. The three men said they would. Mr. Knight said the room would be thirty dollars; ten dollars for each person. Each man gave him the money and then went up to the room.

Mr. Knight soon began to feel sorry. “Thirty dollars is a lot to ask as a price for that small room.” he thought. He called his assistant over and said, “Here is five dollars. Take it to the men in Room 418. I asked too much for their room.”

The assistant took the money. While he was on the way there, he started to think, “How can three men divide five dollars? I’ll give them each only one dollar and keep the two dollars for myself. The men will be happy to get something back. And Mr. Knight will never know.” So the assistant returned one dollar to each man.

Each man had at first paid ten dollars. After the assistant returned them one dollar each, each had actually(in fact) paid nine. There were three men. $9´3="$27." The assistant kept$2. $27+$2="$29." Where is the missing dollar?

小题1:With the help of the manager, the three men___________.

A.went to another hotel

B.each got a small room for the night

C.stayed together in a small room

D.got a small room Mr. Knight kept for himself小题2:At first___________.

A.$27 was paid by the three men

B.$30 was paid by each of the three men

C.$25 was paid by the three men

D.$10 was paid by each of the three men小题3:The assistant___________.

A.helped the men to divide the money

B.kept two dollars for himself

C.kept three dollars for himself

D.returned three dollars to the men and two to the manger小题4:Where is the missing dollar?

A.It was taken by the assistant, too.

B.It was taken by Mr. Knight.

C.It was taken by the three men.

D.In fact, there wasn’t any missing dollar.

题型:不定项选择

酶促反应中决定酶专一性的是

A.酶蛋白

B.辅基或辅酶

C.金属离子

D.底物

E.催化基团

题型:不定项选择

液压传动是在()容器内完成的。

A.密封

B.敞开

C.半封闭

D.随意

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