Which of the following words is closest in meaning to “Indurate”?

Indurate means hardened.

• Correct answer - hardened: it has the same meaning as Indurate.
• flexible: easily bent - wrong, it does not mean the same as Indurate.
• weak: lacking strength - wrong, it does not mean the same as Indurate.
• diligent: hardworking - wrong, it does not mean the same as Indurate.