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London’s First Light Rail System
The Docklands Light Railway (DLR) took just three years to build at a cost of £77 million. It is London’s first Light Rail System, but its route follows that of a number of older lines, which carried the nineteenth century railways through the crowded districts of the East End.
The section of the line from the Tower Gateway Station to Poplar follows the line of one of London’s earliest railways, the London&Blackwell (1840), a cable-drawn railway (later converted to steam) which carried passengers to steam ships at Blackwell Pier, and provided transport for the messengers and clerks who went backwards and forwards between the docks (码头) and the city every day.
From Poplar to Island Gardens, a new line crosses high above the dock waters, and then joins the old track of the Millwall Extension Railway, built to service the Millwall Docks (1868) and to provide transport for workers in the local factories. This line was horse- drawn for part of its route, until the 1880s.
The Poplar to Stratford section of the DLR route was first developed by the North London Railway, built in the 1850s to link the West and East India Docks with the manufacturing districts of the Midlands and North of England. There were major railway works and sidings (岔线) at Bow until recently.
The trains are automatically controlled from a central computer, which deals with all signaling and other safety factors, as well as adjusting speeds to keep within the timetable; on board each vehicle, Train Captains, who are also fully qualified drivers, are equipped with two-way radios to maintain contact with central control. There are passenger lifts, and self-service ticket machines, at every station.
The trains on the DLR are controlled by

A.an on-board central computer.
B.a computer engineer on board.
C.two-way radios operated by the drivers.
D.a computer center based somewhere along the line.
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Which of the following statements about Eta carinae is NOT true A.It will end up as a supernova. B.It can be seen only through binoculars. C.It is the only star that sends out an ultraviolet laser. D.Its ultraviolet laser is brighter than that of the Sun.
As possibly the galaxy’s (银河) most massive star, Eta Carinae is now engaging in some very unusual behaviour. Australian astronomers, being in the Southern Hemisphere (半球), are able to observe it clearly.
In the 19th century, Eta Carinae was for a time the third brightest star in the sky. It has now become less bright so that binoculars (双筒望远镜) are needed to see it. "It seems to be brightening and becoming less bright over a period of many years", said Dr Bob Duncan from the Australia Telescope National Facility.
While it is not unusual for stars to vary in brightness, the period is usually much shorter. "Since 1992 it has become four times brighter, and then last year it began to drop dramatically," he said.
The problem in observing Eta Carinae is that it has been surrounded by a cloud of gas and dust, making it hard to see the star directly. However, radio waves and infrared light (红外线) can pass through this cloud, so telescopes that receive these wavelengths can observe what is occurring.
Eta Carinae is of particular interest to astronomers because it seems to be in its death throes (剧痛). Being so large it will end up as a supernova (超新星). There has not been a supernova in our galaxy since the invention of the telescope. While a 1987 explosion in a nearby galaxy gave astronomers plenty of valuable data, they are hungry for an even closer look.
Eta Carinae has other unique features, and is the only star known to produce an ultraviolet (紫外线) laser that is brighter than that produced by the Sun. Lasers have been observed in other frequencies from a few stars.