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.

A.

The traits are governed by genes on different chromosomes.

If they were not on the same chromosome linkage would occur which will change the ratio

i believe the correct answer from the choices listed above is the first option. the scientists need to look at the   validity of data, claims, hypotheses, and observations before  developing an argument. they base their arguments on facts that are present and they make sure they have proofs. 

explanation:

prism b but im not for sure