Snapping two days of gains, the Sensex at the Bombay Stock Exchange dropped 126 points, or 0.8 percent, to 16,312, amid a weak rupee, and falling Asian and European markets on Wednesday.The Sensex had gained 220 points in previous two trading sessions. The Nifty at the National Stock Exchange declined 39 points, or 0.8 percent, to 4,951.Stock markets in Japan, China, Hong Kong, South Korea and Singapore declined between 0.2 percent and 1.9 percent, on fresh euro zone worries.