<p>The second has a misplaced modifier. The first is in passive voice. However, passive is acceptable at times. The second shouldn't be better than the first.</p>
<p>"Because..." is an adverb clause so it's OK that it's next to "NASA officials." It doesn't modify the noun "officials." it modifies the verb "chose."</p>
<p>p.s. i got a 2390 (790 M) so I am going to say very arrogantly that i'm prob right.. watch me eat my words haha</p>
<p>Based on his exceptionally hardy and well-preserved physique, 77-year-old John Glenn was chosen by NASA officials to participate in a study....</p>
<p>or</p>
<p>Because his physique was exceptionally hardy and well-preserved, NASA officials chose 77-year-old John Glenn to participate in a study..... </p>
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<p>This is actual easier than you guys are making it out to be. The incorrect sentence is sentence 2, not sentence one. What does the beginning phrase of sentence two modify? (Because HIS physique was exceptionally hardy and well-preserved). It modifies JOHN GLEN, and not NASA. Therefore, John Glenn should immediately follow the modifier and not NASA. This error is corrected in sentence 1. </p>
<p>If this doesn't make sense, consider the following two sentences:</p>
<p>1) Because he was strong, the GYM hired BOB as a manager.
2) Because he was strong, BOB was hired by the gym as a manager. </p>
<p>CLEARLY, the latter modifies correctly BOB correctly. ( The GYM was not strong!) </p>
<p>***. It's absolutely obvious the latter is WRONG. It uses "Because" in the beginning of a sentence (the evident giveaway), as well as making the NASA officials sound like they have hardy well-preserved physiques.</p>
<p>dying_ember... i agree with your second point. However, using because in the beginning of a sentence is not gramatically incorrect although 70 % of people on CC would say so. It has been adopted in the english language as legitimate in recent years. (look it up). </p>