Falling for the second straight session, the Sensex at the Bombay Stock Exchange posted its biggest fall in two weeks, of 147 points, or 0.8 percent, to close at a one-week low of 18,349. The Sensex fell as investors adopted a cautions stance amid protests against economic reforms, and weak Asian and European markets, today. The Nifty at the National Stock Exchange fell 46 points, or 0.8 percent, to 5,554. Stock markets in Japan, China, Hong Kong, South Korea and Singapore lost between 0.4 percent and 2.1 percent.