Answer: Option (c) is the correct answer.
Step-by-step explanation:
A covalent bond is defined as the bond formed due to sharing of electrons between the two chemically combining atoms. And, potential energy is defined as the energy present due to the position of atoms or object.
A chemical bond hods potential energy and when atoms move closer to each other then there occurs a decrease in bond length and atoms becomes more fixed at a certain position.
As a result, potential energy of the atoms tend to increase.
Thus, we can conclude that if two covalently bonded atoms move closer than a distance of the bond length, the potential energy of the atoms increased.