A ground-breaking report written by a major group of scientists has in

I choose (E).
"untraceable pollutants" is plural so we must use "many of the previously untraceable pollutants" --> A,B and D out
"many of ... pollutants" must go with "come" - S & V agreement --> C out
So (E) is correct: many of the previously untraceable pollutants in stream water known to kill fish and harm humans come from

E is the answer.

We have a countable noun pollutants. It is not right to modify it with much, which is used to modify uncountable nouns. We can eliminate A, B, and D based on this split.

On the grounds of subject-verb agreement, we can eliminate C for the use of a singular verb comes for the plural noun many of the untraceable pollutants.
E is the right answer.

A ground-breaking report written by a major group of scientists has indicated that much of the previously untraceable pollutants in stream water known to kill fish and harm humans comes from polluted rain water and irresponsible chemical dumping by large corporations.

(A) much of the previously untraceable pollutants in stream water known to kill fish and harm humans comes from
(B) much of the previously untraceable pollutants in stream water known to kill fish and harm humans come from
(C) many of the previously untraceable pollutants in stream water known to kill fish and harm humans comes from
(D) much of the previously untraceable pollutants in stream water known to kill fish and harming humans come from
(E) many of the previously untraceable pollutants in stream water known to kill fish and harm humans come from

Answer is E for using "many' for the countable pollutants and the plural verb "come".

(E) many of the previously untraceable pollutants in stream water known to kill fish and harm humans come from

MEANING: A report indicated that many [a number] pollutants [countable, plural] known to kill fish and harm humans come [plural] from polluted rain water and chemical dumping.

USAGE: "many" is used to express numbers for countable nouns, those with a plural subject; "much" is used to express an amount for uncountable nouns, those without a plural subject.

Ans (E)

Pollutants - Countable noun and Plural form
--> We should use "many " , "not much" --> A, B, D --out.

many of .... pollutants ... come from (not comes from) --CORRECT ONE

(E) many of the previously untraceable pollutants in stream water known to kill fish and harm humans come from

The answer is E.

Much is used for uncountable nouns such as “Pollutants”. Singular verb should be used after pollutants, hence come. IMO B.

Posted from my mobile device

A ground-breaking report written by a major group of scientists has indicated that much of the previously untraceable pollutants in stream water known to kill fish and harm humans comes from polluted rain water and irresponsible chemical dumping by large corporations.

(A) much of the previously untraceable pollutants in stream water known to kill fish and harm humans comes from
(B) much of the previously untraceable pollutants in stream water known to kill fish and harm humans come from
(C) many of the previously untraceable pollutants in stream water known to kill fish and harm humans comes from
(D) much of the previously untraceable pollutants in stream water known to kill fish and harming humans come from
(E) many of the previously untraceable pollutants in stream water known to kill fish and harm humans come from

The two common filters here are many/much and comes/come

many: used for countable nouns and much used for uncountable nouns

pollutants being countable many should be used instead of much hence eliminate A, B and D

Between C and E the only difference is come/comes and is a compound and makes the subject plural hence come should be used instead of comes

IMO E

IMO E:
many of the previously untraceable pollutants in stream water known to kill fish and harm humans come from

A ground-breaking report written by a major group of scientists has indicated that [url]much of the previously untraceable pollutants in stream water known to kill fish and harm humans comes from[/url] polluted rain water and irresponsible chemical dumping by large corporations.

(A) much of the previously untraceable pollutants in stream water known to kill fish and harm humans comes from
(B) much of the previously untraceable pollutants in stream water known to kill fish and harm humans come from
(C) many of the previously untraceable pollutants in stream water known to kill fish and harm humans comes from
(D) much of the previously untraceable pollutants in stream water known to kill fish and harming humans come from
(E) many of the previously untraceable pollutants in stream water known to kill fish and harm humans come from

OFFICIAL EXPLANATION

There are two major issues with the sentence as it was originally written:

(1) This sentence improperly uses much to describe a countable quantity (i.e., pollutants) when many should be used instead. In proper English, much is used for uncountable quantities (e.g., much of the water) while many is used for countable quantities (e.g., many apples, many gifts).

(2) The subject of the sentence (untraceable pollutants, which is plural) does not agree with the verb of the sentence (comes, which is singular).

A. Much is wrongly used to describe a countable quantity when many should be used instead; the subject (pollutants) does not agree with the verb (comes)

B. Much is wrongly used to describe a countable quantity when many should be used instead

C. the subject (pollutants) does not agree with the verb (comes)

D. Much is wrongly used to describe a countable quantity when many should be used instead; the phrase to kill fish and harming humans is not parallel (i.e., to kill is not parallel with harming, which should be harm)

E. Many is correctly used with a countable quantity; the subject and verb are both plural