求教91

mwh9511

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 beeing priced to sell,and have
E. had been priced to sell,and they have
不是很理解其中的DO ,HAVE在句末的用法，为什么它们是一种省略，这种形式是怎么变过来的。缺少它们行吗