One volt is the same as

The correct answer is A. one joule/coulomb.

One volt is the potential difference that will cause a current of one ampere to flow through a resistance of one ohm. In other words, one volt is equal to one joule of energy per coulomb of charge.

Option B is incorrect because one coulomb per joule is equal to one ohm.

Option C is incorrect because one coulomb is a unit of charge, not of potential difference.

Option D is incorrect because one joule is a unit of energy, not of potential difference.