Ashish did not admit his mistake in the beginning.

Answer: Option C

Commit : perpetrate or carry out (a mistake, crime, or immoral act).
Apologize : express regret for something that one has done wrong.
Accept : receive as adequate, valid, or suitable.
Realise : become fully aware of (something) as a fact; understand clearly.
Admit : accept as valid.

Synonym of Admit is Accept