[单选题]轨道车结构特点代号指轨道车传动方式代号。其中，机械传动不标号，液力传动用字母（ ）表示。
A.T
B.Y
C.D
D.G

In 1971 the Royal College of Physicians decided to take action on the problem of smoking and health. They formed an organization called Action on Smoking and Health -- ASH. Its aims are to make people aware of the dangers of smoking and to help those people who do smoke to give up. As part of its campaign to make people see how smoking damages us all, both as individuals and as members of society, ASH has gathered together some every convincing facts and figures. For in stance, smoking is very harmful to industry. Nearly 50 million working days are lost in Britain every year due to smoking -- at least four times the number of days lost in strikes. And the cost of treating people suffering from smoking related disease is around ￡ 100 million each year.
But the human suffering which smoking causes is far more serious than the economic price which society has to pay. 95% of those who suffer from bronchitis are smokers. It has been estimated that 20% of all cigarette
A. Economic losses are the most serious.
B. Human sufferings are more serious than economic losses.
C. More than 20,000 smokers die of bronchitis every year.
D. 95% of those who suffer from bronchitis are smokers.