Final answer:
The word 'frivolity' means a lack of seriousness, making it the antithesis of gravitas, which conveys seriousness and dignity.
Step-by-step explanation:
The word 'frivolity' refers to a lack of seriousness or lightheartedness. It is the opposite of gravitas, which denotes a quality of seriousness and dignity. While gravitas would be related to someone who carries a sense of importance and substance, frivolity often implies a carefree or careless attitude, one that might be found in playful or trivial activities. In the context of the options provided, the correct answer is (2) Lack of seriousness. For example, planning a meticulous and formal dinner party would be an action with gravitas, whereas throwing an impromptu dance party might be considered an act of frivolity.