下列化合物中不参与三羧酸循环的是（）。

A.丙二酸

B.柠檬酸

C.草酰乙酸

D.α-酮戊二酸

E.琥珀酸

In country after country, talk of nonsmoker’s right is in the air. While a majority of countries have taken little (51) no action yet, some 30 nations have introduced legislated steps to control smoking. Many laws have been introduced in other countries to (52) clear the air for nonsmokers, or to cut cigarette consumption.

Smoking is harmful (53) the health of people. World governments should conduct serious campaigns against it. (54) on cigarette advertisements, plus health warnings on packages and ban on public smoking in certain places, (55) as theaters, cinemas and restaurants, are the most popular tools used by nations in (56) of nonsmokers or in controlling smoking. But world attention is also focusing on another step (57) will make the smoker increasingly self-conscious and uncomfortable about his habit. Great efforts should be made to (58) young people especially of the dreadful consequences of taking up the habit. And cigarette price should be raised.

In the long run, (59) is no doubt that everybody would be much better-off if smoking were banned altogether but many people are not (60) for such drastic action.

55().

A.such 

B.even 

C.so 

D.not