Answer:
b. in a direction that makes its potential energy decrease.
Explanation:
A positive charge always moves in the direction of electric field whereas the negative always moves in the direction opposite to the electric field. In both cases the potential energy of the of the charges decreases.
Similar to objects under gravity always tend to decrease their potential energy, charges also, tend in move in the direction so that their potential energy is minimum.
b. in a direction that makes its potential energy decrease.
