Step-by-step explanation:
If both charges are positive, the force will be positive; similarly, if both charges are negative, the force will be positive.
If one charge is positive and another is negative, the force will be negative.
The correct answer is "positive; negative". According to Coulomb's Law, the force between two charges is directly proportional to the product of the charges and inversely proportional to the square of the distance between them. The force is attractive if the charges are of opposite sign (one positive and one negative), and repulsive if the charges are of the same sign (both positive or both negative). Therefore, when one charge is positive and another is negative, the force between them is attractive, while when both charges are positive or both are negative, the force between them is repulsive.