Answer: The correct answer is D) Decreasing the mass of the car.
Explanation-
According to the Newton's second laws of motion, the force acting on a body is equal to the product of mass of the body and the acceleration.
Mathematically, it is written F = ma
⇒ a =

As per the question, the engine is same. It means the action force is constant.
In order to increase the acceleration, the mass of the car will be decreased as acceleration inversely proportional to mass for constant force.
Thus, option D) is the right answer.