The S&P 500 (SPX) and Nasdaq-100's (NDX) narrow leadership has made Tony Zhang "selectively bullish." Expanding market breadth is making him more "constructively bullish." He talks about key levels he believes the S&P and Nasdaq need to hold to solidify bullish expectations. Turning to his example options trades, he sees "cheap" opportunity in Nvidia (NVDA) as the stock approaches an upside target of $270. Tony tilts more bearish in his Citigroup (C) trade.