[求助]GWD-2-34 SC题，没讨论过

吉吉狗

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.

 

1. and whether, presuming such life forms having left fossil traces to begin with, those traces can
2. and whether, if it is presumed that such life forms left some fossil traces to begin with, can those traces
3. and whether, presuming such life forms left fossil traces to begin with, those traces
4. and, presuming such life forms did leave some fossil traces to begin with, if they can
5. and, presuming such life forms to have left fossil traces to begin with, if they

答案是A, C为什么不对？是不是presuming后面的时态left不对？

chnp

一种说法是C的presuming后要加that

becharming

并且，从句子的意思看，can是必要的。