All the given words are verbs.
The word, 'admit' means 'agree/ accept'. The word, 'concede' means 'admit or agree that something is true after first denying or resisting it'. These three words, 'admit', accept' and 'concede' are similar in meanings.
The word, 'deny' means 'state that one refuses to admit the truth or existence of'. As the meaning of this word is different from that of the other words, option C is the correct answer and other options are incorrect.