What is force which causes rocket to take off?

Answer: Taking off of rocket is an example of newton's 3rd law of motion, which states that; action and reaction are equal in magnitude but opposite in direction. The rocket takes off vertically. The fuel and hot gases escape out of rocket's tail with high pressure, this is an action. As a result of propelling force of these gases, rocket moves up, which is the reaction equal in magnitude and opposite in direction.