(C) According to the law of conservation of momentum, the total momentum of the system remains conserved during the collision.
$1$. Kiran's suggestion: The insect experiences a much larger change in velocity compared to the car. Since $p = mv$, the change in momentum $(\Delta p = m \Delta v)$ for the insect is significant relative to its mass. Because the car's mass is massive, its change in velocity is negligible, meaning the insect experiences a greater change in momentum relative to its own state, but the magnitude of momentum change for both is equal.
$2$. Akhtar's suggestion: Akhtar is partially correct that the car exerts a large force, but the force exerted by the car on the insect is equal to the force exerted by the insect on the car (Newton's $3^{rd}$ Law).
$3$. Rahul's suggestion: Rahul is correct. According to Newton's $3^{rd}$ Law, the force exerted by the car on the insect is equal and opposite to the force exerted by the insect on the car. Since the time of impact is the same for both, the change in momentum $(F \times t = \Delta p)$ is equal in magnitude for both the car and the insect.