请大家帮我看看这个语法题

liuzeyu1368

情态动词在这里不能省可以理解，但是这里的插入语：
presuming such life forms having left fossil traces to begin with
始终不知道是什么意思，表达的是什么结构，
如果presume引导的是从句的话，后面的表达好像不完整呀~~

没看懂，请NN解析一下吧。。

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

答案是A

liuzeyu1368

看到一样题目的帖子浮上来了，咋没人帮我做呀@@。。。

jbc88

争议题。。我支持的是C。我那个答案上也是C。

liuzeyu1368

听说GWD给的是A，哎。。纠结