标题: have done 并列，第二个have能不能省略？ [打印本页] 作者: 勒勒了 时间: 2010-5-25 19:27 标题: have done 并列，第二个have能不能省略？ 77. (28689-!-item-!-188;#058&003708) 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. (A) eras, therefore concluding that its crust is harboring up to three times as much water than was (B) eras, therefore concluding that the planet's crust harbors up to three times as much water or more as was (C) eras and have therefore concluded that the planet's crust harbors up to three times as much water as (D) eras and they have concluded, therefore, that its crust harbors up to three times as much water, or more, than (E) eras and concluded, therefore, that the planet's crust is harboring up to three times more water as was