The answer is B: A résumé summarizes your skills and experience, while a cover letter explains how those qualities will benefit the employer.
A résumé, otherwise called CV or curriculum vitae, is a document that summarizes your academic and professional achievements in a chronological order and in general fashion. A cover letter, on the other hand, is a personalized letter (addressed to your potential employer and referencing the open position) in which you state in a formal fashion how those skills relate to the job you are applying to, how the employer would benefit from these skills, and how you would become an asset for the employer.
