Option A) is unquestionably not a question. (So, we cross that out)
Option B) Yeah, of course, he is happy so there should be an exclamation mark. Exclamation shows a loud calling or crying out; outcry; loud or emphatic utterance; vehement vociferation; clamor; that which is cried out, as an expression of feeling; sudden expression of sound or words indicative of emotion, as in surprise, pain, grief, joy, anger, etc.
Option C) He already finished the sentence. So there is no need to add a comma.
So, the answer should be B)
