Answer:
D
Step-by-step explanation:
The correct sentence is D as it contains the right punctuation .The writer is making use of two adjectives conveying opinion in order to describe a person´s smile.It seems that the second adjective is used so as to make the description clearer as to what the meaning of a happy smile is and that is why it is used in the second place.In the other sentences the punctuation is incorrect as those uses do not exist .