The answer is d. Inertia
According to Newton's first law of motion, every body continues to be in a state of rest or of uniform motion unless an external force acts upon it. This is called inertia; the tendency of an object to resist change.
So when the car makes a sharp left turn, the passengers seem to move towards the right side of the car because the passengers continue to maintain the straight line path ahead along which the car was moving before taking the turn