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题库 / Prep2007E2-SC-135
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.
Whereas high speeds generally cannot be achieved by ramjets without their initially being assisted by
Whereas a ramjet generally cannot achieve high speeds without the initial assistance of
With ramjets, high speeds generally are not able to be achieved without initially being assisted by
Unlike with ramjets, generally unable to achieve high speeds without the initial assistance of
Although a ramjet generally does not have the capability of achieving high speeds without the initial assistance from
Similar ideas should, in general, be expressed in parallel constructions.
This is not a grammar issue. Just think about whether the ideas at hand are "bullet points", or "A and B", or "#1 and #2", or whatever.
E.g.,
(A) Ramjets do this.
(B) Scramjets do that.
These make sense as "A and B", or as "two bullet points". So, make them parallel.
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