By Pete Najarian, co-founder of OptionMonsterNEW YORK -- The iShares Silver Trust ( SLV) has been active for months, and upside option activity in the exchange-traded fund is lighting up OptionMonster's systems once again. Calls dominated Thursday's trading as buyers piled into the fund early, according to OptionMonster's tracking systems. The October 34 calls saw more than 9,000 contracts change hands, while the November 35.50 options traded more than 5,000 times. Those calls lock in the price investors must pay to buy shares in the silver ETF, so they can generate some nice leverage with a rally. But these options will expire worthless if the stock doesn't move. The fund rose 1.25% to $33.93 Thursday and is up 23% since early July. It's been holding around these levels more recently, but Thursday's call-buyers don't seem to think that it will stay there much longer. More than 142,000 contracts traded in the session, compared with average volume of about 109,000. Calls outpaced puts by 93,000 to 50,000. Najarian has no positions in SLV.