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

答案选C，不大明白，各位朋友能不能讲讲。。。

The word "do" is referring to sell. The complete sentence is "their wine have been priced to sell, and they do sell." The word "sell" is omitted.