It Is Thought That Attenuation Occurs Especially in a Laboratory

Multiple Choice

It is thought that attenuation occurs especially in a laboratory setting because

A) nonvirulent or weakly virulent mutants grow faster in laboratory media when there is no selective advantage to virulence.
B) pathogens lose virulence with age and survive longer in laboratory cultures.
C) patients can be treated with drugs that induce attenuation.
D) there is selection for more virulent strains in the laboratory.