U.S. stocks closed lower Monday, as investors remained cautious ahead of key decisions out of Europe and the Federal Reserve (Fed). The Dow Jones industrial average fell 52.35, or 0.39 percent, to 13,254.29. The broader Standard & Poor's 500 index dropped 8.84, or 0.61 percent, to 1,429.08. The technology-heavy Nasdaq composite index lost 32.40, or 1.03 percent, to 3,104.02. The dollar gained against the euro, the pound, and the yen. Light sweet crude oil for October delivery fell 12 cents to $96.54 a barrel on the New York Mercantile Exchange. Gold futures dropped $8.70 to $1,731.80 an ounce.