Which One of the Following Best Explains Why People Get

Which one of the following best explains why people get so many colds in their lifetime?

A) The immune system has a hard time identifying the viruses that cause the colds.
B) The viruses that cause these colds constantly produce new antibodies, which cause the symptoms.
C) These individuals do not produce enough white blood cells.
D) The viruses that cause colds evolve rapidly, which results in a change in their antigenic structure.
E) The B cells of these individuals destroy their T cells.