The answer to this question is a because co-sign means to share responsibility. This definition eliminates both options b and c. The reason that it is a is because you are co-signing a lease for the <em>apartment</em>. The apartment lease has absolutely nothing to do with paying for moving expenses, because the lease applies only to the building itself, not your means of transportation to get there.
A representative character is one who stands for D, 'humanity in general'. Because it doesn't stand for only a certain type of personality, an ethnic or a political group, but rather for the whole humankind.
