Which group lists all the abstract nouns in this sentence? The safety of the passengers is the concern of William J. Snow, the pilot, and everyone at TWA.

- Safety, Concern.

Explanation:

Abstract nouns are exemplified as the naming words or nouns that denote an abstract or immaterial thing like an idea, feeling, quality, emotion, or any other intangible idea or concept contrary to physical or concrete object.

In the given sentence, the group of words that exemplify the abstract noun are 'safety and concern' as they they both denote either abstract situation ('safety') or a feeling (concern). Both these words demonstrate immaterial states that do not contain physical existence and exist abstractly. Thus, 'safety, concern' group is the answer.