关于助动词的补出 请斑竹回答一下 看了论坛贴还有几道题不明白

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

The answer is C.

这句话是怎么平行对称的没看明白 而且为什么补DO

the development of a new jumbo rocket that is expected to carry the united states into its next phase of space exploration will be able to deliver a heavier load of instriments into orbit than the space shuttle and at a lower cost.

A the development of a new jumbo rocket that is expected to carry the united states into its next phse of space exploration will be abe to deliver a heavier load of instruments into orbit than the space shuttle and at a low cost

B The development of a new jumbo rocket is expected to carry the united stated into its next phase of space exploration and be able to deliver a heavier load of instruments into orbit at a lower cost than the space shuttle

C the new development of a jumbo rocket, which is expected to carry the united states into its next phase of spaceexploration, will be able to deliver a heavier load of instruments onto orbit at a lower cost than the space shuttle

d a newly developed jumbo rocket, which is expected to carry the united states into its next phase of space exploration, will be able to deliver a heavier load of instruments into orbit than the space shuttle can, and at a low cost

e  a newly developed jumbo rocket, which is expected to carry the united stated into its next phase of space exploration, will be able to deliver a heavier load of instruments into orbit than the space shuttle and to cost less

答案是D 不是很明白E为什么不对 而且助动词怎么补的是CAN?

么人回答嘛～～