Respuesta :
In order to strengthen this argument, the author should consider adding:
D) Survey results that indicate students who did have a complete service hour requirements felt the requirement was a positive and beneficial experience.
In order to strengthen an argument, the author should try to include evidence that supports his or her claim. Data and expert's opinions are great external sources that help strengthen an argument. Data speaks for itself and tends to be an unbiased source that can reaffirm the author's claim.