What type of morphemes change the meaning but not the part of speech of a word?

Inflectional morphemes are the correct choice because they modify a word to convey grammatical information without altering its part of speech. For example, adding an inflectional morpheme like "-s" for plural nouns (e.g., "cat" to "cats") or "-ed" for past tense verbs (e.g., "walk" to "walked") changes the form of the word to indicate tense, number, or comparison, but the fundamental meaning and part of speech remain the same.

In contrast, derivational morphemes often change the meaning and may also change the part of speech of a word, as seen when adding the suffix "-ness" to the adjective "happy," transforming it into the noun "happiness." Compound morphemes involve combining two or more morphemes to form a new word, which can also lead to changes in meaning and often results in a shift in part of speech as well. Prefix morphemes are a specific type of derivational morpheme added to the beginning of a word, which can change its meaning but may also lead to variations in part of speech.