Snapping three days of gains, the Sensex at the Bombay Stock Exchange declined 71 points, or 0.3 percent, to close at 21,255, on profit-booking by investors, and falling regional markets, today. The Sensex had climbed to a record high yesterday. The Nifty at the National Stock Exchange fell 31 points, or 0.5 percent, to 6,333. Stock markets in Japan, Hong Kong, South Korea and Singapore declined between 0.3 percent and 1 percent.