Jan 10 (Reuters) - Canada's main stock index dropped at open on Thursday, retreating from a four-week high, with energy shares leading declines amid lower oil prices.
* At 9:30 a.m. ET (14:30 GMT), the Toronto Stock Exchange's S&P/TSX composite index .GSPTSE was down 44.99 points, or 0.3 percent, at 14,759.74.