OG12 Q87 关于省略

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
C为答案
对于这道题OG的解释是：
In the underlined segment，the second verb does not need to repeat the word sell because it is understood from the previous verb phrase priced to sell,however ,the second verb must be correctly conjugated with the understood sell, they are sell is not a correct verb form;they do sell is correct.
它是想说：In an effort to reduce their inventories, Italian vintners have cut prices;their wines are priced to sell, and they do （sell）这两个sell形式上一致，所以选择C。
但是，在看《新编英语语法》的时候，关于省略有这样一段话：
被省略的动词，可在时，体上与已经出现的相应动词不一致，由此它还举了例子：
bob has not written his report,but he will soon (written his report)括号里面的是省略的部分。
为什么OG的解释和语法书上的正好相反呢，真相到底应该是什么样子的？请牛牛赐教了～～谢谢