讨论的不是as...as...的情况，而是as单单解释为“像”的时候，og里有解释说as后一定加句子，但是作题的时候看到一些例外。
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
71. The original building and loan associations were
organized as limited life funds, whose members made monthly payments on their share subscriptions, then taking turns drawing on the funds for home mortgages.
(A) subscriptions, then taking turns drawing
(B) subscriptions, and then taking turns drawing
(C) subscriptions and then took turns drawing
(D) subscriptions and then took turns, they drew
虽然不是出题点，但是不是可以认为as的这种用法不是必错选项？ | 
