重度慢性牙周炎的确诊指标有（） A.牙周袋深度＞6mm B.附着丧失≥3mm C.牙

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     Cyril was a small town. The houses there were all made of wood; almost everything in the houses were made of wood, too. And all the houses faced south. The town was never peaceful. Fire broke out once

a week on summer afternoons. People were puzzled who was the real firebug (纵火犯).

     One day a big fire broke out. It was said that a Negro(黑人) had jumped out of the house on fire, so

the police arrested all the Negroes in the street. However, there were fires breaking out when the Negroes were in prison.

     Mauson, a physics teacher, didn't believe that the Negroes were the firebugs, and decided to find out

who the real firebug was. One day, he was invited to drink in a pub and happened to notice that many

bottles and plastic plates were baked by the hot sunrays. Suddenly he realized what the actual fact was.

He dashed out of the pub to his friend's house nearby, which also faced south. He made an experiment

there to prove his idea.

     The next Saturday afternoon, Mauson asked some policemen to come to the house. They were told

that the real firebug would be shown there. At that time, the sun was shining full into the house and it

became hotter and hotter inside the room. "Now," said Mauson, "this house will soon catch fire." People

looked at each other in surprise. Mauson asked them to look at the bottles and focus on the table cloth.

After a while the cloth gave off a burning smell and began to catch fire!

     The mystery of fire was discovered, but the police wouldn't believe him and insisted that Negroes had

been the firebugs. Instead they arrested Mauson and put him into prison. But Mauson said he would never turn against science.

1. The town was never peaceful, for fire broke out ________.

A. on Sundays  

B. on summer afternoons    

C. at any time  

D. on winter mornings

2. Why did the police arrest all the Negroes?

A. Because one of them had been seen to set on a fire.

B. Because they were suspected to be the firebugs.

C. Because the police hated the Negroes.

D. Because the Negroes knew something about the fires.

3. Drinking in a pub, Mauson realized ________.

A. he needed to leave the pub

B. he needed to back the bottles

C. it was too hot in the pub          

D. who was the real fire bug

4. By making an experiment, it was proved that the real firebug was ________.

A. the Negroes    

B. bottles      

C. sunrays      

D. plastic plates

5. What happened at the end of the story?

A. The Negroes were set free.

B. The police arrested the real firebugs

C. Mauson was arrested too.

D. Mauson made friends with the Negroes

北京旧城的建筑和街道呈[ ]

A．扇形

B．放射状

C．棋盘状

D．条带状

小红在做了如图所示的实验，弹簧测力计和细线的重力及一切摩擦不计，物重G= 1N，则弹簧测力计A和B的示数分别为

A、1 N，0

B、0，1N

C、1N，1N

D、2N，1N

温燥与凉燥的临床表现有何异同？