Electric boats have eliminated the noise pollution that conventional

The sentence isn't parallel. The correct verb phrase should be ...eliminated....and reduced. This helps us cancel out option A, B and C.

D. reduced the loathsome discharges of oil that fouled American rivers and lakes, to threaten fish and bird life.
-INCORRECT. ....to threaten usage is incorrect here.

E. reduced the loathsome discharges of oil that fouled American rivers and lakes, threatening fish and bird life.
CORRECT. 'threatening....' clearly refers to the discharge of oil to American rivers and lakes.

IMO answer is option E

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Reduced should be parallel to eliminated.
Threatening is modifying the previous Clause.
So E is the right answer IMO

Posted from my mobile device

+1st split: parallelism "eliminated" and "reduced", because of this split, we eliminate A, B & C
+2nd split: "threatening" & "to threaten". "threatening" modifies "the loathsome discharges of oil ", so we eliminate "to threaten".----->E is the correct answer.

MEANING
"Boats have eliminated [past]… AND reduced [past]… that fouled…, threatening [pres-part modifier]…" to maintain parallelism both actions must be in the same tense, and the modifier must show how the rivers are fouled

Answer (D)

___________________________________



E



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Breaking the sentence –
Electric Boats(subject 1 - plural) have eliminated (verb 1, present perfect - plural) the noise pollution(object 1) that(relative pronoun referring to pollution) conventional powerboats(subject 3) made(verb 3 – simple past) and(conjunction) reduce(verb 2 simple present - plural) the loathsome discharges of oil(object 2) that (relative pronoun referring to object 2) foul(verb 4 – simple present) American rivers and lakes(object 3), threatening fish and bird life(verb + ing modifier).

The meaning of sentence is that Electric boats did two things first they eliminated pollution made by conventional powerboats, second they reduced discharges of oil so these must be parallel using ‘and’. Further the sentence presents the problem associated with the discharge of oil which was threatening the fish and bird life.

A. reduce the loathsome discharges of oil that foul American rivers and lakes, threatening fish and bird life. – WRONG. Simple Past of verb ‘reduced’ must be there instead ‘reduce’ so S – V mismatch.
B. reduce the loathsome discharges of oil that foul American rivers and lakes, threaten fish and bird life. – WRONG. Similar S - V error as that of option ‘A’. Also ‘threaten’ acts as a third verb(plural) or plural subject ‘Electric Boats’ so the option changes the meaning of the sentence.
C. reduce the loathsome discharges of oil that foul American rivers and lakes, to threaten fish and bird life. – WRONG. Similar S - V error as that of option ‘A’. Intentional verb ‘to threaten’ changes the meaning of the sentence as fouling would cause problems for fish and bird life.
D. reduced the loathsome discharges of oil that fouled American rivers and lakes, to threaten fish and bird life. – WRONG. Simple Past of verb ‘reduced’ is matched and parallel to eliminated. Intentional verb ‘to threaten’ is similar an error as that of option ‘C’.
E. reduced the loathsome discharges of oil that fouled American rivers and lakes, threatening fish and bird life. – CORRECT. Simple Past of verb ‘reduced’ is matched and parallel to eliminated. Modifier ‘threatening fish and bird life’ properly modifies previous clause implying proper meaning.

IMO Answer (E).

Electric boats have eliminated the noise pollution that conventional powerboats made and reduce the loathsome discharges of oil that foul American rivers and lakes, threatening fish and bird life.

A. reduce the loathsome discharges of oil that foul American rivers and lakes, threatening fish and bird life.
B. reduce the loathsome discharges of oil that foul American rivers and lakes, threaten fish and bird life.
C. reduce the loathsome discharges of oil that foul American rivers and lakes, to threaten fish and bird life.
D. reduced the loathsome discharges of oil that fouled American rivers and lakes, to threaten fish and bird life.
E. reduced the loathsome discharges of oil that fouled American rivers and lakes, threatening fish and bird life.

First split

Have eliminated and have reduced. So ABC gone.

Between D&E, it's not their intention to threathen the bird life, it's a result. Hence verbing is more appropriate.

Posted from my mobile device

Electric boats have eliminated the noise pollution that conventional powerboats made and reduce the loathsome discharges of oil that foul American rivers and lakes, threatening fish and bird life.

Eliminated.......and should be parallel, ... Acting as gerund modifying the last sentence.


Option E correctly uses reduced to make it parallel to eliminated and using ING modifier to previous sentence

Official Explanation

Correct Answer: E

The best answer is E. The form of the word reduce is governed by first verb phrase because it continues in a parallel construction: Have eliminated.. and reduced.

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