Answer:
Option A. Difference in elevation
Step-by-step explanation:
Gravitational force is different in the different locations. It's true.
Gravitational force is inversely proportional to the square of the distance from the center of the earth.
g ∝

When we are at equator, gravitational force is less as compared to the poles. (Since poles are nearer to the center of the earth than equator)
Option A. is the answer.