A divergence in the volume shows chances of a pullback to continue the upwards movement! 17500 was a strong psychological resistance acc. to option chain which was broken today by good movement and there has been a heavy call OI build up qt 18000, suggesting some Call Writing in heavy quantity which indicates a psychological resistance at that level according to the option chain. Do not underestimate the pullbacks in a trend! Go for CE and hold the positions until expiry or until it reaches 18000.