Let's solve this through process of elimination. We know the first part isn't a question, because there are no words to indicate that. Answer choice D is out. Answer choice B doesn't make much sense either, because it doesn't show any end quotation mark to finish off a statement. Answer choice C, a comma, can not fit into this either, because there would have to be an "and" or something similar after the word "town". The only choice left is answer choice A. "The manager will be out of town; he won't be back until Monday."
Using short sentences makes the author sound rude. using run-on sentences makes the author seem super talkative. I suggest use medium length sentences to set the tone.
