According to Coulomb’s law, which pair of charged particles has the lowest potential energy?

a. A particle with a 1- charge separated by 150 pm from a particle with a 2+ charge.

b. A particle with a 1+ charge separated by 150 pm from a particle with a 1+ charge.

c. A particle with a 1- charge separated by 100 pm from a particle with a 3+ charge.