This website gives a really good explanation.
http://web.uvic.ca/~mbest1/engl366c2005/merchant1.html
The answer is: C The aftereffects of combat on soldiers during war
Answer:
They sat and listened to the speech. This is a simple sentence with compound verbs. This answer has been confirmed as correct and helpful. ... "They sat" = independent(simple), "listened to the speech" = dependent..
