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
正确答案是C，我选D，我觉得C有两个whether似乎有重复的感觉 所以没选
可是答案却是C?