Explanation:

- Antonym Explanation of "Antediluvian":

- "Antediluvian" describes something very old or outdated, often referring to a time before the biblical flood.

- Option 1 - Celebrated:

- "Celebrated" means famous or well-known. It doesn't relate to time or modernity, so it's not the correct antonym.

- Option 2 - Isolated:

- "Isolated" means separated or detached. It doesn't relate to age or up-to-date ideas, so it’s not the right choice.

- Option 3 - Subtle:

- "Subtle" means understated or not obvious. Again, this doesn’t contrast with being old-fashioned.

- Option 4 - Modern:

- Modern means current or recent, offering a direct contrast to something ancient or outdated.

- Correct Answer: Modern