Explanation:

Let’s break this down:

- Pensive means being deep in thought or reflective—someone who’s lost in serious, sometimes sad, contemplation.

- Option 1: Frivolous — This means not serious, silly, carefree. It’s almost the opposite of being deep or thoughtful. It’s about being lighthearted when maybe you should be serious.

- Option 2: Unreflective — This means not thoughtful, not given to reflection. It doesn’t necessarily mean silly; it just means you don’t think deeply.

- Option 3: Hollow — Means empty, lacking substance or depth, but not exactly the opposite of thinking deeply.

- Option 4: Goofy — Silly, playful, but not really the direct opposite of pensive.

So here’s the thing: The best antonym for "pensive" is frivolous because it captures that sense of being light and carefree rather than weighed down by thought. "Unreflective" is close, but "frivolous" nails the opposite energy.

Correct answer:

Option 1: Frivolous