Answer:
The correct answer is A. subject.
Step-by-step explanation:
The word "Mick" is being used as the subject of the sentence, which is the person, animal or object that performs the action (eat).
Proper nouns, such as names, are used to replace a pronoun in a sentence and to add clarity to it by specifying who or what is doing the action shown by the verb. In this case, "He" is replaced by "Mick."