A) from cause to effect

B) from effect to cause

C) from effect to effect and on to cause

D) from effect to cause and on to another effect

3. A necessary cause is ____.

A) one without which it is impossible for the effect to occur

B) one of the causes that can produce the effect

C) one that is enough to make the effect occur

D) none of them

注：第三段，A选项是必须在场的相同意思的改写。B选项是原因之一，sufficient cause，C选项没有"必须"含义。

Causes are classified as necessary, sufficient, or contributory（起辅助作用的）. A necessary cause is one which must be present for the effect to occur, as combustion (燃烧)，is necessary to drive a gasoline engine. A sufficient cause is one which can produce an effect unaided (独自的), though there may be more than one sufficient cause: a dead battery is enough to keep a car from starting, but faulty spark plugs（火花塞）or an empty gas tank will have the same effect. A contributory cause is one which helps to produce an effect but cannot do so by itself, as running through a red light may help cause an accident, though other factors --- pedestrians (行人) or other cars in the intersection-must also be present.