The answer is the first choice The character is not insane but he believes he is
The sentence that does not contain any errors in comma usage is option C. Mick introduced me to his dog, a golden retriever. We used a comma after the word dog because the phrase "a golden retriever" serves as an additional information to the sentence.
Definition:Sentence fragments are groups of words that look like sentences, but aren't.
Example:Which is why I cried.
This sentence could be corrected by removing "which is why." The sentence "I cried." is a complete sentence. I is the subject, cried is the action.The sentence could also be corrected by joining it with an independent clause. I was sad, which is why I cried.