Answer:
B. shift to a lower gear
Explanation:
Gears are meant to produce different levels of force when connecting the car and the tires, and this creates the movement of the car, you need different kinds of output torques when changing gears, the initial gears produce more torque to set the car from a stand position into movement, the later gears produce less torque but more revolutions to create more speed, so when going up hill you will need more torque than before because the force necessary to go up is larger than in a flat surface, so you would need to shift to a lower gear.
