Which one of the following statements concerning mumps is correct?

A. Because there is no vaccine against mumps, passive immunization is the only means of preventing the disease
B. Although the salivary glands are the most obvious sites of infection, the testes, ovaries, and pancreas can be involved as well
C. The diagnosis of mumps is made on clinical grounds because the virus cannot be grown in cell culture and serologic tests are inaccurate
D. Second episodes of mumps can occur because there are two serotypes of the virus, and protection is type specific