再问og129

129. In an effort to reduce their inventories, Italian vint­ners have cut prices; their wines have been priced to sell. and they are.

(A)  have been priced to sell, and they are

(B)  are priced to sell, and they have

(C)  are priced to sell, and they do

(D)  are being priced to sell, and have

(E)   had been priced to sell, and they have

In choice C, the best answer, do is correctly used in place of the full verb do sell; in this verb, do is a conjugated form and sell is in the infinitive form, corresponding to its previous use in the sentence (in the phrase priced to sell).

看了以前的讨论，有个地方还是不明白，解释中do is correctly used in place of the full verb do sell，那么还原就是。。。。and they do sell意思是“这些酒确实卖得很好。”但是in this verb, do is a conjugated form and sell is in the infinitive form，这句话又说do是一个什么形式，sell在不定式中，怎么理解呢？

我查了字典，也搞不太懂a conjugated form 。按字典上的说法，to conjugate: To inflect (a verb) in its forms for distinctions such as number, person, voice, mood, and tense.

说do是a conjugated form，我想是do根据时态有不同的形式，如过去式是did.  这里do相当于do (to)sell的省略形式，如果用did, 则did=did (to) sell。

可能我表述不清

这里do (sell)不是强调，而是省略。sell就是前面的to sell，而补全不是do to sell, 而是do加原形。do (to) sell不是do to sell=do sell这里加to不定式没有特别意思，只是表示动词的原形(我们单独引用一个动词原形时，习惯是to do而不仅仅说do)。这种省略在Gmat中还是比较常见的。

看了所有的讨论贴，还是对OG的解释糊里糊涂的，看了上面的解释才恍然。