()的色散度为0.044。A、锆石  B、金刚石  C、紫金  D、砾石

题型:单项选择题

问题:

()的色散度为0.044。

A、锆石 

B、金刚石 

C、紫金 

D、砾石

考点:贵金属首饰手工制作工贵金属首饰手工制作工题库
题型:单项选择题

Buses are celebrating their 100th anniversary. About 80 percent of all public-transport passengers worldwide are carried by buses.

The bus is a very efficient mode of transport, being cheap, flexible, comfortable and, in many cases, tailored to the needs of users both in terms of capacity and speed. Buses operate in mixed traffic, and are easy to put in service.

From an economic, environmental and social point of view, the bus remains the best solution to the problem of achieving balanced and environmentally-friendly urban development. Indeed, the bus is the only mode of public transport in many of the world’s cities, and plays a key supporting role in cities with rail transport.

Over the past decades, increased use of roads by private cars has contributed to terrible traffic problems, affecting the speed of buses as well, and hence their service quality, reliability, energy consumption, and economy. In such circumstances, the efficiency and performance of buses depends heavily on special lanes. Various forms are possible----from a mere painted mark on the road to more expensive variants such as elevated lanes, movable barriers, and “bus locks”.

A related trend is to look beyond vehicle technology alone and to consider the wider system, of which buses are a part, such as the infrastructure(基础设施)and other operational aspects of city. This is commonly known and promoted as the “bus-system approach”. Other key innovations(革新) include clean engines, alternative fuels, and guidance devices. In terms of the designs of buses, much of what has happened to light rail can be transferred to them, including the shapes of the vehicles themselves.

The energy consumption of a bus per passenger is one-sixth that of a car, and buses are only responsible for about 5% of the CO2 emissions generated by vehicles at present.

1. From this passage we learn that_____________.

A. buses are the most environmentally-friendly of all motorized vehicles

B. buses were first used more than a century ago

C. most passengers prefer trains to buses

D. a bus has a much larger capacity than any other vehicle

2. What has affected the service quality of buses?

A. Unsuitable infrastructure.                      B. Private cars.

C. The increasing population of cities.

D. Very rapid urban development.

3. Which of the following is an approach to improving bus service?

A. Improving the speed of buses.

B. Reducing the number of private cars.

C. Setting up special lanes for buses.

D. Increasing the number of buses.

4. From the passage we can infer that in the future_____________.

A. there will be more buses than today

B. bus engines will need no power

C. buses will be replaced by other means of transport

D. the appearance of buses will change

题型:单项选择题

如图所示,MN和PQ是水平光滑的导轨,ab为垂直搁在导轨上的导体棒,它们的电阻都可忽略不计.竖直的匀强磁场穿过导轨平面,导轨的左端与一电路连接,图中R1=5Ω,R2=15Ω,R3为滑动变阻器,伏特表的量程为0~20V,安培表的量程为0~3A.请完成下列问题:

(1)当滑动变阻器阻值调节为30Ω,ab棒向右匀速滑动时,两个电表中有一个满偏,另一个处于正常状态,请问是哪一个电表的指针满偏?另一个电表的示数是多少?

(2)在(1)题的情况下,若ab棒所受向右的水平拉力大小为20N,求ab棒匀速运动的速度大小;

(3)若ab棒在30N的水平拉力作用下匀速运动,为了使两个电表都能正常工作,求滑动变阻器的电阻值的变化范围.

题型:单项选择题

定王的六世孙开创东汉王朝,请问这位开国皇帝的姓名。

题型:单项选择题

下列各项中,哪些属于产品质量法所称的“产品”()

A.棉布

B.经济适用房

C.面粉

D.活鱼

题型:单项选择题

非法拘禁致人死亡的,( )。

A.构成故意伤害罪

B.构成故意杀人罪

C.构成非法拘禁罪

D.应当以非法拘禁罪从重处罚

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