Explanation:

- Radiance refers to brightness or light reflected or emitted by something. It conveys a sense of shining brilliance or glow.

- Option 1: Brilliance - This word implies an intense brightness or vividness. It is a synonym of radiance, not an antonym.

- Option 2: Glow - Glow suggests a steady and soft light, similar to radiance. It is also aligned with the concept of light and cannot be an antonym.

- Option 3: Dullness - Dullness indicates lack of brightness, shine, or light. It is the opposite of radiance, making it the correct antonym.

- Option 4: Glitter - Glitter describes a sparkling or shimmering effect, akin to radiance. It is not an antonym.

- Correct Answer: Option 3 - Dullness