In a Vaccine Such as Menactra, What Is the Main

In a vaccine such as Menactra, what is the main purpose of linking the capsular polysaccharides of Neisseria meningitis to the diphtheria toxin?

A) To stimulate a T cell-dependent immune response
B) To eliminate infections that commonly occur together
C) To add another vaccine to reduce the number of injections a patient receives
D) To prevent destruction of the polysaccharide antigens before an immune response can be mounted