Snapping three days of gains, the Sensex at the Bombay Stock Exchange dropped 108 points, or 0.6 percent, to 16,713, on profit-booking by investors, amid falling global markets on Monday.The 30-share Sensex had surged more than 970 points in the past three trading sessions. The Nifty at the National Stock Exchange declined 23 points, or 0.5 percent, to 5,017.Stock markets in Japan, China, Hong Kong, Singapore and South Korea were hammered down by between 2 percent and 4.5 percent, on global growth concerns.