The Sensex at the Bombay Stock Exchange closed with a marginal gain of 13 points, or 0.1 percent, at 19,255, on Monday, amid cautious trade by investors. The Nifty at the National Stock Exchange rose 8 points, to 5,856. Stock markets in China, Hong Kong, South Korea and Singapore posted small gains between 0.1 percent and 0.3 percent.