有1.5L的C2H4和C2H2组成的混合气体，恰好能与同条件下的2.7L的H2完

某物体体积2米³，质量是5.4×10³千克，则这个物体的密度是________千克/米³。

Mrs Lane was strict ______ very nice. [ ]

A. but

B. and

C. or

D. so

患者，女性，40岁，因“胆囊炎，胆囊结石”在全麻下行LC术，既往有支气管哮喘病史二十年，在麻醉苏醒期发生了幻觉、谵妄，该患者在麻醉期间使用了下列药物，考虑该患者的幻觉、谵妄现象与哪种药物有关（）

A．麻黄碱

B．氯胺酮

C．芬太尼

D．维库溴胺

E．布比卡因

Bicycles are a great way to get around. They’re fun to ride, especially down hills. And, as you speed along the road, you might also think of ways in which you could improve your bike— make it safer, more efficient, or more comfortable. In fact, the two-wheeled machines make for some cool science projects.

This year's Intel International Science and Engineering Fair (ISEF), held last May in Cleveland, featured（had）three bicycle projects from three countries. Like many of the other experiments presented at ISEF, the bike projects showed that some of the most interesting scientific research often begins by taking a closer look at things you care about.

Renato Angulo Chu had even grander ambitions. The 12th-grader from Lima, Peru, wanted to address some of his country's economic troubles.

"I see a problem in my country," Renato said. "If you go to the forests in Peru, in some places you cannot find electricity. If you go with my bicycle, you can turn on the lights."

Renato, 16, spent 3 years designing his special Multibike. The device looks like a fixed exercise bike. It has wires fixed along the frame and a blender strapped(fastened) to the back. Turning the pedals operates the blender. The same principle can be used to sharpen knives or sweep city streets.

The Multibike can work either as a fixed bike or as a bicycle able to travel city streets and country roads. It's made from inexpensive materials, and the user gets exercise while pedaling to operate a machine.

"You pedal the bike, and you can mix any drink you want," Renato said. More importantly, he added, the same concept could be used to bring light to houses in remote regions of the rainforest.

19. What can we learn from the first paragraph?

A. Bicycles are the best way to go about

B. Bikes should be made more comfortable to ride.

C. You can improve your bicycle for science research.

D. Many inventions are connected with the bicycle.

20. Which of the following is true according to the passage?

A. ISEF is an exhibiton displaying bicycle experiments designed by students.

B. Looking closely at things you are concerned about can lead to scientific research.

C. Renato’s improvement of the bicycle has solved the country’s great problem.

D. Renato’s special bicycle will soon be put into use in remote areas.’

21. The underlined word “address” in the third paragraph probably has the same meaning as _______.

A. make address written        B. give up             C. work at             D. speak at

22. Renato’s special Multibike has all the following EXCEPT  ________.

A. making knives sharp                                     B. mixing any kind of drinks

C. producing electricity                                     D. operating a machine with its own electricity

23. It can be inferred that Renato’s special bicycle is mainly designed for ________.

A. distant areas in the rainforest without electricity.

B. the use of his own family to make life easier.

C. the competition of ISEF to win money to support remote rainforests

D. enough exercise by pedaling it

洁治术的目的是（）

A.使牙齿漂白

B.清除牙面烟斑

C.清除龈上牙石和菌斑

D.去除袋内菌斑生物膜

E.清除受毒素污染的根面牙骨质