By David Russell, reporter at OptionMonsterNEW YORK -- The bulls are coming back to the China shop, looking for a rally in e-commerce stock Sina ( SINA). OptionMonster's tracking programs detected the purchase of 10,000 December 80 calls for $1.88 and the sale of 10,000 December 90 calls for 78 cents. There was virtually no open interest in either contract before the trade appeared, so this is a new position. Buying calls locks in the entry price for a stock, while selling them obligates a trader to unload shares at a certain level if they are above it. In the case of Wednesday's transaction, the trader has the right to buy the stock for $80 and then must sell it for $90 if it's over that higher price. The trader paid $1.10 for that $10 spread. Sina closed Wednesday at $64.38, up 1.23%. Although it would have to rally about 40% to reach $90, the option strategy would leverage that move into a profit of more than 809%. The stock is trying to rebound from a major pullback that erased more than two-thirds of its value between April 2011 and July 2012. The last earnings report on Aug. 15 beat expectations, and management remained positive on monetizing its Weibo microblogging service. Overall option volume was more than triple the daily average in the name Wednesday, with calls outnumbering puts by 5 to 1. Russell has no positions in SINA.