6631. He was not able to unearth his secret to the last.

✅ The correct answer is option B.
Suppress : forcibly put an end to.

Discover : find unexpectedly or during a search.

Disclose : make (secret or new information) known.

Decode : convert (a coded message) into intelligible language.

Unearth : discover (something hidden, lost, or kept secret) by investigation or searching.

Synonym of Unearth is Discover