GWD 2-34

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

B,D,E一来就能排除...

presume朗文里面没有那个用法..

表示假设的时候就这三种用法：

presume that
I presume we'll be there by six o'clock.
presume somebody/something to be somebody/something
From the way he talked, I presumed him to be your boss.
be presumed to do something
The temple is presumed to date from the first century BC.

不包括A的用法，而且whether can这个逻辑意思好像不对的，不是说它是否可能，而是说它是否留下痕迹...这个状语从句用得真是没话说...

是不是选C？

怎么我的GWD里面没这题...楼主是哪个版本啊...

  我的GWD 给的答案是C.

请教一下：

b选项，不看后面，“if it is presumed that such life forms left some fossil traces to begin with” 是否正确？

c选项，presuming这个分词……主语是谁呢？