Two Normal Individuals Have a Child Who Has Cystic Fibrosis,an

Multiple Choice

Two normal individuals have a child who has cystic fibrosis,an autosomal recessive disease.How did this happen?

A) The mother had two recessive alleles.
B) The mother had one recessive allele and one normal allele,and the father had two normal alleles.
C) The mother had two normal alleles,and the father had one recessive and one normal allele.
D) Each parent had one normal and one recessive allele.
E) Both parents had two normal alleles.