Which of the following examples illustrates a free morpheme?

A free morpheme is a word that can stand alone and still convey meaning, as opposed to a bound morpheme, which cannot stand alone and must be attached to a free morpheme to convey meaning. In the options provided, "fire" is a free morpheme because it is a complete word on its own. It represents a specific concept and does not require additional morphemes to establish its meaning.

In contrast, the other options—"re," "un," and "anti"—are all examples of bound morphemes. They are prefixes that modify the meanings of other words but cannot function independently. For instance, "re" implies repetition or going back, "un" indicates negation, and "anti" suggests opposition. Each of these must be attached to a base word to convey a meaningful concept. Therefore, "fire" stands out as a free morpheme because it is fully formed and carries its own meaning.