A)the cold virus mutates so people have no immunity.
B)they get a chill.
C)many different viruses cause the common cold.
D)antibiotics don't kill viruses.
E)they haven't been vaccinated.

A)Haemophilus influenza.
B)Bordetella pertussis.
C)Corynebacterium diphtheria.
D)Streptococcus pyogenes.
E)Streptococcus pneumoniae.

A)is most frequently caused by Corynebacterium diphtheriae.
B)is a life-threatening condition requiring urgent intubation.
C)occurs predominantly in the elderly.
D)is known as croup.
E)may spread throughout the body causing systemic effects.