请教三个问题．．．．

stephenep

1. After more than four decades of R&D, a new type of engine is being tested that could eventually propel aircarft anywhere in the world within two hours or help boost cargoes into space at significantly lower cost than current methods permit.

A　tested that could eventually propel aircarft anywhere in the world within two hours or help

D  tested, and it could eventually have the capability to propel in the world within two hours or help

why choose D instead of A? Ａ不是定语后置吗？

2. A new hair-growing drug is being sold for three time the price , per milligram, as the drug's maker chargs for another product with the same active ingredient.

A as 

B than

C that

D of what

E at which

这题更奇怪了，答案是D，可是不是定语从句吗

3. Fossils of the arm of a sloth found in Puerto Rico in 1991, and dated at 34 million years old, made it the earliest known mammals of the Greater Antilles island.

A sloth found in Puerto Rico in 1991, and dated at 34 million years old, made it the earliest known mammals of

C sloth that was found in Puerto Rico in 1991, was dated at 34 million years old, making this the earliest known mammal of

D sloth, found in Puerto Rico in 1991, have been dated at 34 million years old, making the sloth the earliest known mammal on

E sloth which, found in Puerto Rico in 1991, was dated at 34 million years old, made the sloth the earliset known mammal of

我选Ｄ，答案是Ｃ，但是Ｃ用that was结构不是变成定语从句修饰sloth吗？事实上修饰的应该是化石？如果Ａ OF b结构的词定语从句改优先修饰哪个呢？谢谢！

遥远的绿洲

发问题贴的时候请一个帖子问一个问题,这样方便大家讨论,谢谢