Answer:
D
Step-by-step explanation:
D is the only correctly-punctuated sentence of them all. A is almost incomplete, as there are 2 ideas joined in a single sentence without even a comma to separate them (even though the ideal thing would be a period after "veterans." B is almost correct, but the comma that follows "syndrome" should either be replaced by a semi-colon or a period, or the next sentence should start with a lead-in like "as." C is correct up until the second comma, where a new idea is introduced; this new idea should be introduced as a new sentence, with either a period or a semi-colon. D is the correct use of the semi-colon, as it separates a different idea from the first one, but not so much as to put a period between them.