bryan88 wrote:As a result of a supernova explosion, every human being on Earth was bombarded on February 23, 1987, by about 100 billion neutrinos; fortunately, neutrinos are harmless elementary particles that are produced in nuclear reactions and that interact very weakly with matter.

2nd part of the original sentence intends to say 'how Neutrinos are produced' and 'how they interact with matter'

(A) neutrinos are harmless elementary particles that are produced in nuclear reactions and that

THAT verb....and THAT verb (do not find any problem)

(B) neutrinos, which are harmless, are elementary particles produced in nuclear reactions and which

NEUTRINOS ARE PARTICLES...(INDEPENDENT CLAUSE) AND WHICH interact (RELATIVE CLAUSE). It's a run-on sentence. The part after AND does not have an independent clause. Generally, if we have one part of AND a relative clause, the other part should also be relative cluase. That is, WHICH....AND WHICH... (would be ok)

(C) neutrinos are harmless elementary particles produced in nuclear reactions and which

same as B

(D) these harmless elementary particles are produced in nuclear reactions, and neutrinos

THESE HARMLESS PARTICLES do not have a clear referent - does it refer to NEUTRINOS? We can't say. Furthermore, this choice changes the original meaning: original sentence says 'neutrinos are harmless elementary particles' and it also says "neutrinos/partciles are produced in nuclear reactions". But this choice does not conveys that NEUTRINOS ARE HARMLESS PARTICLES - IT DOES NOT SHOW ANY RELATIONSHIP WITH "ELEMENTARY PARTICLES".

Moreover we do not know why AND is used - it is just connecting the 2 independent clauses...but we do not know whether there is any relaionship btn these two clauses that warrant connecting them with AND - I do not find any logical reason to make them PARALLEL

(E) these elementary particles, harmless products of nuclear reactions, are neutrinos that

changes the orginal meaning

IMO A

A +1

A...For Correct parallelism and pronoun reference. Rest all have parallelism errors or pronoun referrent isseues.