May 18 (Reuters) - Canada’s main stock index was flat in early trade on Tuesday, as gains in gold were countered by a drop in oil prices, while investors were optimistic of demand recovery after the reopenings of the U.S. and European economies. * At 9:40 a.m. ET (13:40 GMT), the Toronto Stock Exchange’s S&P/TSX composite index was up 7.03 points, or 0.04%, at 19,481.68. (Reporting by Shivani Kumaresan in Bengaluru; Editing by Ramakrishnan M.) Our Standards: The Thomson Reuters Trust Principles.