Several Vaccines Are Combination Vaccines and Are Used to Vaccinate

Several vaccines are combination vaccines and are used to vaccinate people against two or more pathogens.One example of a combination vaccine is the TDaP vaccine (tetanus, diphtheria, and pertussis) .How does a combination vaccine develop immunologic memory to more than one pathogen?

A) Allergic reactions are less common with combination vaccines than with single-antigen vaccines.
B) Combination vaccines develop immunity against very similar or the same (broad spectrum) antigens.
C) Combination vaccines are more economical to produce than single vaccines.
D) Each antigen target included in the combination vaccine must be different enough so that the immune system can recognize the target antigen on the pathogen cell.
E) Similar antigens can be chemically modified so that the immune system will recognize each antigen as unique.