若f（x）在R上可导，f（x）=x2+2f′（2）x+3，则∫03f（x）dx=

下列有关碳循环的叙述中正确的是[ ]

A．光合作用是CO₂进入生物群落的唯一途径

B．动物细胞的无氧呼吸是大气中CO₂的产生途径之一

C．没有分解者，碳循环仍可保持平衡状态

D．初级消费者用消化系统摄入生产者合成的含碳有机物

.Life gets noisier every day and very few people can be free from noise of some sort or another. It doesn't matter where you live--in the middle of a modern city, or a faraway village--the chances are that you' 11 be disturbed by jet planes, transistor radios, oil - powered engines, etc. We seem to be getting used to noise, too. Some people feel quite lonely without background music while they' re working.

Scientific tests have shown that total silence can be a very frightening experience for a human being. However, some people enjoy listening to pop music which is very loud, and this can do harm to their eardrums(耳鼓). The noise level in some discos is far above the usual safety level for heavy industrial areas.

One recent report about noise and concentration(专心) suggested that although a lot of people say that any noise disturbs their concentration, what really influences their ability to concentrate is a change in the level of noise. It goes on to say that a background noise which doesn't change too much(music, for example) may even help people to concentrate.

56. According to this passage, the noise pollution __

A. has become the worst in the countryside  B. has become better in big cities

C. has spread from cities to villages      D. has been controlled in modern cities

57. What does background music refer to?

A. Music played while people are working.   

B. Music played in the backyard.

C. Noise that continues while you' re listening to other noises.

D. Music used to help people to concentrate.

58. Some people have their hearing harmed __

A. while listening to pop music            B. in complete silence

C. when speaking loudly                  D. while watching TV

59. Which of the following isn't included among the things causing noise?

A. trucks           B. motorcycles   C. electric engines   D. jet planes

60. Scientists have discovered that what prevents people from concentrating on something is

A. all kinds of noise                   B. great changes in the level of noise

C. background noise                  D. popular music          

火府丸功效与作用

机械密封的泄漏，其中压盖与密封箱体、轴套与轴表现为静密封的泄漏。

对于气象雷达，测试结果有ATT信息，说明（）

A.表示测试时天线的故障

B.表示测试时面板故障

C.表示收发机故障

D.表示姿态输入故障