What state of matter has molecules that are closest together?

The correct answer is solid because in solids, the molecules are packed closely together in a fixed arrangement. The strong intermolecular forces hold the molecules in place, which restricts their movement. This close proximity of molecules enables solids to maintain a definite shape and volume.

In liquids, the molecules are still close together but can move past one another, allowing liquids to take the shape of their container while retaining a fixed volume. In gases, the molecules are farther apart, moving freely and occupying the available space, which results in no fixed shape or volume. Plasma, while not typically encountered in daily life, consists of ions and free electrons and behaves similarly to gases but at extremely high temperatures where molecules are also widely spaced apart. Therefore, solids clearly have the closest arrangement of molecules compared to the other states of matter.