Prep sentence

straw520fish · 发表于 2011-10-20 20:36:40

135.(31919-!-item-!-188;#058&006548)

Whereas high speeds generally cannot be achieved by ramjets without their initially being assisted by a rocket, a scramjet, or supersonic combustion ramjet, can attain high speeds by reducing airflow compression at the entrance of the engine and letting air pass through at supersonic speeds.

(A) Whereas high speeds generally cannot be achieved by ramjets without their initially being assisted by

(B) Whereas a ramjet generally cannot achieve high speeds without the initial assistance of

(C) With ramjets, high speeds generally are not able to be achieved without initially being assisted by

(D) Unlike with ramjets, generally unable to achieve high speeds without the initial assistance of

(E) Although a ramjet generally does not have the capability of achieving high speeds without the initial assistance from

Anybody can tell why there is no "it" in the second part of the sentnce?

Prep sentence

所属分类: GMAT考试

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