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题库 / Prep2007E1-SC-77
Scientists have found signs that moving water changed the chemical makeup of the surface of Mars in recent eras, therefore concluding that its crust is harboring up to three times as much water than was previously thought.
eras, therefore concluding that its crust is harboring up to three times as much water than was
eras, therefore concluding that the planet's crust harbors up to three times as much water or more as was
eras and have therefore concluded that the planet's crust harbors up to three times as much water as
eras and they have concluded, therefore, that its crust harbors up to three times as much water, or more, than
eras and concluded, therefore, that the planet's crust is harboring up to three times more water as was
还没有题目讲解（毕出老师会陆续发布对官方考题的解读，请保持关注）。
可以放在have前面。therefore这里属于副词，作状语。状语的位置非常灵活，放在句子的任何地方都是可以接受的。登录 或 注册 后可以参加讨论
错选B，在一道题里，如果只有分词ing的形式不同，那么通常从句＋动词的形式>分词ing形式，因为可以更清晰的表达时态的变化。
C正确，have found 和 have concluded平行
1.副词≠连词。SVO，therefore,SVO 错！排DE。
2.concluding 表伴随错，排AB。
3.选C
more ... as ... / as ... than ... / more ... compared with
more... rather than / rather... more than
BE少than错，
"was" is ok.it's not necessary, though, because "previously" is there. so, the sentence is more efficient without it.
of course, nothing in the last post really matters for this exam, which will NEVER task you with stylistic ('good writing' / 'bad writing') decisions.for the gmat exam, the only things that matter are......it's acceptable to write 'have' twice, and ...it's also acceptable to omit the second 'have' (unless that omission creates a genuine ambiguity).
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所以！！做SC的时候，要确定正确答案之前一定要仔细的核对（带着句意去理解评估）