The answer is B: So you can provide information that relates directly to the audience´s needs.
A cover letter is a personalized document in which you address a specific audience in relation to a vacancy or an open job position, that is to say, it is usually addressed to a potential employer. It usually accompanies your CV, but unlike the CV, it is not a list of your professional and academic achievements, rather it is a composition of statements that relate to the audience´s specific needs and how they would benefit from employing you as well as how you can contribute further to their objectives.