<p>"John was carrying a heavy pack, which caused him to sweat a lot."</p>
<p>Conservatively, using a relative clause to modify a phrase with a verb is grammatically incorrect. However, this particular usage is pretty common. Would this be viewed as correct for the SAT?</p>
<p>Normally I'd think it would be fine, but I just read a practice question where "X happened, explaining Y." was incorrect, so I'm not sure how much of a stickler they are.</p>