A Key Factor in the High Prevalence of Otitis Media

A key factor in the high prevalence of otitis media in children is

A) the orientation of the eustachian tube in children prevents efficient fluid drainage.
B) the lack of a mature microbiome in the auditory canal.
C) children are more likely to suffer from colds and influenza than adults.
D) children do not complete their routine vaccine schedule until adolescence.
E) the maturing of the innate and adaptive immune responses in children.