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题库 / GMATLA-SC-9
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.
and whether, presuming such life forms having left fossil traces to begin with, those traces can
and whether, if it is presumed that such life forms left some fossil traces to begin with, can those traces
and whether, presuming such life forms left fossil traces to begin with, those traces
and, presuming such life forms did leave some fossil traces to begin with, if they can
and, presuming such life forms to have left fossil traces to begin with, if they
比较ABC，当中whether, xxxx, yyyy， 这个xxx结构暂时不看
所以三个结构式
A.and whether those traces can
B.and whether can those traces
C.and whether those traces
B的结构错误，verb在subject前面，没有必要倒桩
则AC的区别就是是否应该存在这个can. 所以看前半句whether biological life forms ever emerged on Mars
动词是emerged，所以这里应该用exist，而不是can，这里不是情态动词平行
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