By Pete Najarian, co-founder of OptionMonsterNEW YORK -- Options have been strong across the financial sector, and Tuesday the activity accelerated in Citigroup ( C) . The April calls stood out the most on OptionMonster's tracking systems, especially the April 41s, with buyers coming in for 47 cents to 52 cents. More than 9,000 contracts changed hands at that strike. Those calls lock in the price investors must pay to buy shares in the megabank. That makes them highly leveraged to upside in the stock, but they will expire worthless if there is no rally. Citigroup shares rose 2.45% to $38.08 Tuesday and are up 47% in the last three months. Almost 227,000 options traded in the name Tuesday -- more than triple the normal amount. Najarian own C calls and shares.