Potential energy and kinetic energy, roughly speaking are counterparts, when we have a lot of kinetic energy, we have a lot of movement and therefore a very low potential energy, but if we have a very low kinetic energy, which means almost no movement whatsoever, therefore we will have a high potential energy.
For our question, we are looking for the state that has the lowest amount of kinetic energy, which means the lowest amount of movement, which will be the Solid state. Letter A