-The Figure Above Represents a Pedigree for a Family in Which

-The figure above represents a pedigree for a family in which dark-shaded symbols represent individuals with one of the two major types of colon cancer.Numbers under the symbols are the individuals' age at the time of diagnosis.A slash through the symbol indicates that the individual is deceased.In each generation of this family after generation I,the age at diagnosis is significantly lower than would be found in nonfamilial (sporadic) cases of this cancer (~63 years) .What is the most likely reason?

A) Members of this family know to be checked for colon cancer early in life.
B) Hereditary (or familial) cases of this cancer typically occur at earlier ages than do nonfamilial forms.
C) This is pure chance;it would not be expected if you were to look at a different family.
D) This cancer requires mutations in more than this one gene.