Shares of Fort Worth-based RadioShack surged as much as 33 percent in morning trading after a trader spent more than $600,000 buying bullish options.About 20,000 calls expiring in October with a strike price of $1.50 were purchased, according to Trade Alert LLC. The stock (ticker: RSH) then surged, reaching $1.75 a share in the biggest intraday advance since at least 1980. The shares closed up 13 cents, or nearly 10 percent, at $1.45. “Somebody’s taking a big bullish bet on the stock,” said Alex Panagiotidis, managing director for equity derivatives at Sterne Agee & Leach Inc., a Birmingham, Alabama-based brokerage firm. “This trade helped push the stock higher.” RadioShack has sank to its lowest point in decades this year after a dispute with lenders blopcked its plan to close as many as 1,100 underperforming stores. The company said earlier this month that it would only be able to close a smaller number because it couldn’t get consent from creditors. The stock is down 40 percent this year. In march, the struggling consumer electronics retailer said its fourth-quarter net loss widened to $191.4 million, marking the eighth consecutive quarterly deficit. Sales at stores open at least a year sank 19 percent in the period. Spokeswoman Merianne Roth declined to comment on the stock activity this morning.RadioShack’s $1.50 October calls were the most-traded options today, according to data compiled by Bloomberg. The contract jumped 18 cents to 43 cents and has tripled in value since May 22. The rally may have forced short sellers to close bearish positions and purchase the stock, said Mark Neuman, managing director of derivatives trading at JonesTrading Institutional Services in New York. About 22 percent of the shares have been borrowed and sold to speculate on future losses, according to data compiled by Markit Ltd. There was “a huge technical level at $1.50, which had been the lid on RSH for the past month,” Neuman said in an interview. “Once that got taken, the stock ran right up.” RadioShack is scheduled to hold its annual shareholder meeting on Tuesday and announce quarterly results seven days later. The retailer will probably say that its first-quarter loss widened to 49 cents a share from 35 cents a year earlier, analyst estimates compiled by Bloomberg show. The options market is implying a one-day move of 22 percent after the report.