May 19 (Reuters) - Canada’s main stock index fell at open on Wednesday, dragged down by energy stocks as oil prices fell on demand concerns due to a deepening COVID-19 crisis in Asia, while a rise in annual inflation rate in April also weighed. * At 9:31 a.m. ET (13:31 GMT), the Toronto Stock Exchange’s S&P/TSX composite index was down 203.71 points, or 1.04%, at 19,303.34. REporting by Shivani Kumaresan in Bengaluru; Editing by Vinay Dwivedi Our Standards: The Thomson Reuters Trust Principles.