Final answer:
Students who use and understand idioms, similes, and metaphors are employing their knowledge of semantics, the aspect of language concerned with meaning. Syntax, phonemes, and morphemes relate to sentence structure and word formation, not the interpretation of figurative language.
Step-by-step explanation:
Students who use and understand idioms, similes, and metaphors are using their knowledge of semantics. Semantics deals with the meaning of words and phrases in a language and how these meanings are interpreted. In contrast, syntax refers to the arrangement of words and phrases to create well-structured sentences.
Idioms are expressions whose meanings are not predictable from the usual meanings of their constituent elements or from the general grammatical rules of a language. For example, 'it's raining cats and dogs' doesn't mean that pets are falling from the sky, but rather it's raining very heavily. Similes and metaphors are figures of speech that compare different things: a simile uses 'like' or 'as' (e.g., 'as brave as a lion'), while a metaphor makes the comparison directly (e.g., 'he's a lion in battle'). Both similes and metaphors go beyond literal meanings to give readers new insights.
Phonemes and morphemes, on the other hand, are related to the sounds of the language and the smallest units of meaning within words, respectively. They do not directly apply to the interpretation of idioms, similes, or metaphors. Therefore, the correct answer to the question is d) Semantics.