Which sentence does not contain any punctuation errors? A. This is definitely the most important moment of my life so far? B. This is definitely the most important moment of my life so far! C. This is definitely the most important moment of my life so far,

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)

B, as the person is excited.

It is not A as they are not asking a question, they are making a statement

It is not C as they have used a comma meaning that there should be another sentence after it.