Question

how do seatbelts act within the system to counter this effect and keep passengers safe?
seatbelts absorb the cars energy to keep the passengers in motion.
seatbelts provide an opposite force that opposes the passengers forward motion.
seatbelts reduce the cars velocity to match that of the passengers.
seatbelts provide a balanced force that stops the forward motion of the passengers.

Explanation:

According to Newton's laws of motion, during a sudden stop or collision, passengers tend to move forward due to inertia. Seat - belts work by providing an opposing force to counter this forward - motion tendency. They don't absorb the car's energy to keep passengers in motion (this is incorrect as they aim to stop the motion), don't reduce the car's velocity to match the passengers' (the car's velocity change is due to external forces like braking or collision), and don't provide a balanced force to stop motion (balanced forces result in no acceleration, but seat - belts act as an unbalanced force to decelerate the passengers).

Answer:

B. Seatbelts provide an opposite force that opposes the passengers' forward motion.