When two average-height parents give birth to a child exhibiting achondroplasia, it is most likely due to a new mutation. This is because:
a) the frequency of achondroplasia is unknown
b) achondroplasia is a relatively rare disorder
c) achondroplasia is caused by an allele that is always expressed, therefore the parents must not have the allele
d) such mutations are statistically predictable
e) none of the above
