Points to consider:
- do the expressions "brought about" and "brought on" have similar meaning?
- are any answer choices unnecessarily long?

A can be eliminated for awkward construction: starting with two modifying phrases ("Brought on..." and "besides...") Additionally, "brought on..." should be describing "muscle atrophy", but they are at opposite ends of the sentence.

B is better, but the placement of "in protracted space flight" is odd. It appear to only describe "radiation", and I'm not sure that's the intended meaning.

C has the same double-modifier problem as A, and I think "brought about through" is awkward and incorrect.

D has two modifying phrases as well, but in this case they're not that bad (using a relative clause to modify "hazards"). The second half of the sentence, though, is awkward and overly wordy.

E is a good answer. It is very similar to B with two key differences. First, "in protracted space flight" is used to modify "astronauts", which makes more sense in the context of the hazards. Second, "muscle atrophy brought on by weightlessness" is more direct than B's "muscle atrophy, which is brought on by weightlessness."

Bill@VeritasPrep wrote:A can be eliminated for awkward construction: starting with two modifying phrases ("Brought on..." and "besides...") Additionally, "brought on..." should be describing "muscle atrophy", but they are at opposite ends of the sentence.

B is better, but the placement of "in protracted space flight" is odd. It appear to only describe "radiation", and I'm not sure that's the intended meaning.

C has the same double-modifier problem as A, and I think "brought about through" is awkward and incorrect.

D has two modifying phrases as well, but in this case they're not that bad (using a relative clause to modify "hazards"). The second half of the sentence, though, is awkward and overly wordy.

E is a good answer. It is very similar to B with two key differences. First, "in protracted space flight" is used to modify "astronauts", which makes more sense in the context of the hazards. Second, "muscle atrophy brought on by weightlessness" is more direct than B's "muscle atrophy, which is brought on by weightlessness."

thanks bill for you help

E makes sense

I was with B until I read option E.

Definitely option E is good answer.

Is B wrong because of radiation in protracted space flight . Does it sound like hazards meteors and rocky debris are not applicable to space flight but just radiation?