Final answer:
The correct option is 'a. Mass.' According to Newton's second law of motion, the acceleration of an object is directly proportional to the net force applied to it and inversely proportional to its mass.
Step-by-step explanation:
The correct option is a. Mass.
According to Newton's second law of motion, the acceleration of an object is directly proportional to the net force applied to it and inversely proportional to its mass. In the case of a rocket, a smaller mass will result in a greater acceleration during launch.
For example, if two rockets are launched with the same force but one has a smaller mass, the rocket with the smaller mass will experience a greater acceleration.