Given below is a word, followed by three sentences which consist of that word. Identify the sentence(s) which best express(es) the meaning of the word. Choose option 5 ‘None of the above’ if the word is not suitable in any of the sentences.

ENIGMA

A: The food that he ate filled his heart with sheer enigma. 

B: His brother's death under mysterious circumstances was still an enigma to him. 

C: He knew his dog so well and what he was going to do next was already an enigma to him.