Which of the following is NOT an example of an antonym?

An antonym is a word that has the opposite meaning of another word. In the context of the choices provided, the first, second, and fourth pairs each consist of words that clearly express opposing concepts—such as temperature in "Hot - Cold," light and absence of light in "Light - Darkness," and emotional states in "Happy - Sad."

In contrast, "Fast" and "Quick" are synonyms; they share a similar meaning and describe something that occurs in a short amount of time or at a high speed. Since these words do not exhibit opposing meanings, this pair does not represent an antonym. Understanding the difference between synonyms and antonyms is key to grasping the relationship between words, which is essential for expanding vocabulary and comprehension in reading.