The fact that all seven of the pea plant traits studied by Mendel obeyed the principle of independent assortment most probably indicates which of the following?
a. None of the traits obeyed the law of segregation.
b. The diploid number of chromosomes in the pea plants was 7.
c. All of the genes controlling the traits were located on the same chromosome.
d. All of the genes controlling the traits behaved as if they were on different chromosomes.