TT-2-34 求教

Q34:

NASA’s methodical approach to the exploration of Mars has not yet answered the questions of whether biological life forms ever emerged on Mars and whether, presuming such life forms having left fossil traces to begin with, those traces can still exist in some moist recesses of the cold and arid planet.

A.    and whether, presuming such life forms having left fossil traces to begin with, those traces can

B.     and whether, if it is presumed that such life forms left some fossil traces to begin with, can those traces

C.     and whether, presuming such life forms left fossil traces to begin with, those traces

D.    and, presuming such life forms did leave some fossil traces to begin with, if they can

E.     and, presuming such life forms to have left fossil traces to begin with, if they

   Answer: A

I THINK C IS RIGHT.

A虽然看着别扭， 字典好像也没有presume ...doing的用法

不过C的 presuming 后面y应该加一个that

no best answer? thanks, anyway.