Coulomb's law predicts that: a. like charges attract b. like charges repel c. unlike charges repel d. none of the above

Let us consider two charges . They are separated by distance r.

As per coulomb's law, the force of attraction or repulsion between two charges are directly proportional to the product of two charges and inversely proportional to the square of separation distance between them.

Mathematically  

Here, is called as the permittivity of the medium.

If the two charges are either positive or negative, the force will be positive. It means that the force is repulsive. Hence, like charges will repel each other.

If the two charges are opposite in sign, then the force will be negative. Hence, unlike charges will attract each other.

Hence, the correct answer to the question will be b: like charges repel.