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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
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B为什么不对啊
"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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