Falling for the second straight session, the Sensex at the Bombay Stock Exchange has dropped 146 points, or 0.7 percent. It closed at 20,709 on Wednesday amid rising crude oil prices, and weak Asian markets. The Nifty at the National Stock Exchange fell 41 points, or 0.7 percent, to 6,161.Stock markets in Japan, Hong Kong, South Korea and Singapore lost between 0.9 percent and 2.2 percent.