Since Many Childhood Diseases Such as Mumps and Measles Are

Since many childhood diseases such as mumps and measles are rare now within the United States, why is it still important for children to be immunized against them?  

A) If we lose herd immunity by removing mandatory vaccination, our population will become susceptible to these illnesses again in a short period of time.
B) There is always the likelihood that an individual from another country could import one of these illnesses into the United States, sparking an outbreak of new infections, if we aren't all properly vaccinated.
C) By keeping the population vaccinated, we keep incidence rates of these illnesses very low. This helps to protect people that cannot be vaccinated (very young children, pregnant women, immunocompromised individuals, the elderly) .
D) Many of these diseases are HIGHLY contagious, and commonly through respiratory droplet (airborne) transmission. This makes an outbreak within a susceptible population very possible. Keeping the population resistant through mandatory vaccination prevents this possibility.
E) All of the options are correct.