By Pete Najarian, co-founder of OptionMonsterThe U.S. Natural Gas Fund ( UNG) is drawing large trades that are apparently counting on its shares to rise 20% in the next five months. More than 31,700 calls traded at the Oct. 20 strike yesterday, dwarfing the average volume of 523 contracts, according to OptionMonster's tracking programs. The calls included two large blocks -- one of 4,000 contracts and the other of 22,000 -- trading at $1.45 within seconds of one another Thursday. The vast majority of the calls, which were nearly five times the open interest at that strike, were bought at or near the ask price. Those factors suggest that these trades were new positions with a bullish bias. The exchange-traded fund has been rising in recent weeks but is still not far from its 52-week low of $12.69 hit just April 30. It's about one-fourth of the way to its $63.89 high from last July. The shares closed Thursday up 1.5% to $16.68.