Answer The third sentence effectively uses a semicolon. A semicolon is used to separate two independent clauses, or complete sentences, that are closely related in meaning. In the third sentence, "Ihsan walked the dog today" and "they got incredibly muddy when the dog ran into the puddle" are both independent clauses, and the semicolon is used correctly to separate them.
In contrast, the other sentences in the list do not use the semicolon correctly. In the first sentence, the semicolon is used to separate a clause that is not independent, "Isa is extremely excited for the movie to open this weekend," from a phrase, "A huge fan of the author." In the second sentence, the semicolon is used to separate two clauses that are not closely related in meaning, "As a student in the course, Neive is nervous about one thing" and "the course reading." In the fourth sentence, the semicolon is used to separate a clause that is not independent, "Zayan is incredibly proud of his mom," from a noun, "a neurobiologist."
Therefore, the correct answer is "Ihsan walked the dog today; they got incredibly muddy when the dog ran into the puddle."