[求助]GWD-8-Q34、39: 在讨论帖上没有见到有这道题

虽然通过排除法得到答案D，但是不是特别明白。请NN指点。

GWD-8-Q34: GWD-13-28

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 mammal of the Greater Antilles islands.

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

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

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

B.       sloth, that they found in Puerto Rico in 1991, has been dated at 34 million years old, thus making it the earliest mammal known on

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 earliest known mammal of

GWD-8-Q39:

Whereas in mammals the tiny tubes that convey nutrients to bone cells are arrayed in parallel lines, in birds the tubes form a random pattern.

     
   A.      Whereas in mammals the tiny tubes that convey nutrients to bone cells are arrayed in parallel lines, in birds the tubes

B.       Whereas the tiny tubes for the conveying of nutrients to bone cells are arrayed in mammals in parallel lines, birds have tubes that

C.      Unlike mammals, where the tiny tubes for conveying nutrients to bone cells are arrayed in parallel lines, birds’ tubes

D.      Unlike mammals, in whom the tiny tubes that convey nutrients to bone cells are arrayed in parallel lines, the tubes in birds

E.       Unlike the tiny tubes that convey nutrients to bone cells, which in mammals are arrayed in parallel lines, in birds the tubes