[单选题]轨道电路区段无车占用，轨道继电器落下(开路式)或吸起(闭路式)，轨道电路这种状态就是（）状态。
A.调整
B.开路
C.短路
D.分路

Text 2
The biggest danger facing the global airline industry is not the effects of terrorism, war, SARS and economic downturn. It is that these blows, which have helped ground three national flag carriers and force two American airlines into bankruptcy, will divert attention from the inherent weaknesses of aviation, which they have exacerbated. As in the crisis that attended the first Gulf War, many airlines hope that traffic will soon bounce back, and a few catastrophic years will be followed by fuller planes, happier passengers and a return to profitability. Yet the industry’s problems are deeper—and older—than the trauma of the past two years implies.
As the centenary of the first powered flight approaches in December, the industry it launched is still remarkably primitive. The car industry, created not long after the Wright Brothers made history, is now a global industry dominated by a dozen firms, at least half of which make good prof
A. Governmental restrictions are still imposed on aviation industry in many areas.
B. Governments help establish rules for aviation industry only in America and Europe.
C. Some countries hope to help their national carriers keep up their national prestige
D. Many countries discourage merger plans between foreign and domestic carriers.