Agood sample should be changed in the middle of your experiment to add variety guarantees your experiment has no problems expands your choices of who to study allows you to generalize results

Which of the following accounts for someone who has had regular herpesvirus-mediated cold sore or genital sore flare-ups? a) re-infection by a closely related herpesvirus of a different strainb) re-infection by the same herpesvirus strainc) copies of the herpesvirus genome permanently maintained in host nucleid) copies of the herpesvirus genome permanently maintained in host cell cytoplasm