68. Often visible as smog, ozone is formed in the

atmosphere from hydrocarbons and nitrogen oxides, two major pollutants emitted by automobiles, react with sunlight.

(A) ozone is formed in the atmosphere from

(B) ozone is formed in the atmosphere when

(C) ozone is formed in the atmosphere, and when

(D) ozone, formed in the atmosphere when

(E) ozone, formed in the atmosphere from

我想問的是D

可不可以句子還原成:

ozone, often visible as smog, formed in the atmosphere when ....???

我不知道D錯在哪裡

选D的话，这个句子就没谓语啦。如果这时候你把formed看成谓语的话，那么D就变成主谓之间用逗号分隔，这个是错误的。

这个问题我当时也想了一下, OG说的比较模糊, 就说没有谓语, 但是考试的时候正常的思维是究竟要不要加上这个is呢?

我的想法是, 遵从原句, 如果原句是被动, 则去掉be就是缺谓语, 如果原句是主动, 是否需要变成被动就自己判断了.

这个考点提示我们对原句的表达要十分注意, 尤其是在拿不准的情况下.