Final answer:
The correct answer is d) Neither. The words 'badinage' and 'echelon' are used in the sentence, but they are not subjects. The subject is the person who is acutely embarrassed by his blunder.
Step-by-step explanation:
The correct answer is d) Neither. The words 'badinage' and 'echelon' are used in the sentence, but they are not subjects of the sentence. They are used to describe the subject's attempts at casual conversation. The subject is the person who is acutely embarrassed by his blunder. In this case, the subject is not 'badinage' or 'echelon' but the person whose attempts at casual (badinage, echelon) did not conceal the fact that he was acutely embarrassed.