Steven Had Mumps as a Child

Multiple Choice

Steven had mumps as a child.Why did he not experience symptoms at the age of 41 after he was again exposed to the mumps virus?

A) He had an injection with weakened virus shortly before he was exposed.
B) He had natural passive immunity to ward off the virus.
C) He had artificial passive immunity that he received from his brother after he had the mumps.
D) He developed active immunity as the result of having mumps as a child.