Gregor Mendel proposed the law of independent assortment based on the observation that dihybrid crosses of heterozygous individuals produced progeny in a 9:3:3:1 ratio. For this observation to hold, which assumption must be true?
A.
The traits are governed by genes on different chromosomes.
B.
The traits are governed by genes on the same chromosome.
C.
The traits are governed by genes with only two alleles.
D.
The traits are governed by genes with only three alleles.