当行业处于发展阶段的后期和经济周期的低位时，企业所面临的竞争程度( )。A．最小

下面四组词中，只有一组加粗字的读音完全正确是[ ]

A．一摇一晃（huǎng）　   调（diào）动

B．落（luò）下残疾　　　结（jié）果

C．查（zhā）老师　　　　给（jǐ）予

D．恶（wù）作剧　　　　暑假（jià）

North American back bears are shy animals. They are fearful by nature, and will usuallyrun away if they see or hear people. Because of this, it can be difficult for scientists to learnabout these animals.

In order to study black bears, researchers from New Jersey, USA, catch bears and usedrugs to help them go to sleep. Researchers then work out the size and the weight of the bear,take blood to test for diseases, remove a tooth and take it to the lab to find out its age. Fromthese studies,researchers want to find out how many bears live in New Jersey, how long theylive, and how many babies theyproduce.

But in Minnesota, USA, researchers study bears that are completely awake. The bears knowthe researchers' voices and they are not afraid of die research team. With the help of a few grapes

to keep the bears busy, researchers can touch them to check their hearts, look at their teeth, and do other jobs.Researchers can also walk or sit with bears for hours and make videos to learn about their everyday lives.

In both places, the main purpose is the same—to make sure there is a healthy population of black bears. But theresearch methods and the kinds of information that researchers, are able to collect are quite different.

小题1:In the first paragraph, we can learn that North American black bears are _______.

A．shy and fearful animals

B．not found today

C．well known to scientists

D．not afraid of people小题2:The word "remove" in the second paragraph probably means _____ in Chinese.

A．拔下

B．移植

C．清洗

D．修补小题3:Which of the following may NOT be included in the New Jersey studies on bears?

A．The age.

B．The way of their communication.

C．The weight.

D．The number of babies they produce.小题4:In the Minnesota studies, researchers _____.

A．can never get close to the bears

B．study the bears while they are asleep

C．use grapes to make the bears full

D．learn a lot about the bears' everyday lives小题5:What do the two studies have in common?

A．Research places.

B．The main purpose.

C．Research methods.

D．Collected information.

阀门安装方法有误，安装（）应注意介质流向。

A、闸阀

B、截止阀

C、旋塞阀

D、止回阀

光信号能够在光纤中以极低的损耗传输是利用了光纤的（）原理。

A.反射

B.折射

C.全反射

D.透射