涛涛GWD31-02-34

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

我也选C， 同意ProfCPA的看法，但没有找到presuming合适的例句。感觉having和can多余。

C: presume sth. done ,wrong

or presume (that), lack of that

beside, add "can" and no "can" has different meaning. So A