The correct answer is A. simple subject.
Subject is a word, phrase, or even a clause, that does the action within a sentence, or experiences some sort of state. There are different types of subjects:
1. simple subject - consists of one word only; in the sentence above, the subject is the word Melinda
2. complete subject - contains all words connected to the simple subject; if the underlined part of the sentence was Melinda, a college student from Maine, then it would be a complete, rather than a simple subject
3. compound subject - contains more than one subject, connected with the conjunction and; for example, Melinda and Bob