Final answer:
The grammatical concept that compares two things using adjectives is the 'comparative of adjectives.' It utilizes forms like 'more' or adding '-er' to an adjective, altering its function in a sentence to express comparison. The correct option is d) Comparative of adjectives.
Step-by-step explanation:
The grammatical concept that refers to the form of adjectives used to compare two or more things, indicating a higher or lower degree of the quality described, is the comparative of adjectives. This form is used to show whether something has a greater or lesser degree of a particular quality in comparison to something else. For example, in the sentence 'Ms. Chu needs to find a more reliable car,' the adjective 'reliable' is being compared in a greater degree by the use of the comparative word 'more,' making it part of the comparative adjective phrase.
Recognizing the form versus function of words is important in understanding grammar. While the form of a word is its part of speech, the function is how it behaves in a sentence. Comparative adjectives are an example where the adjective takes on the function of comparing two nouns.