Mendel observed a 9:3:3:1 ratio of offspring when studying different traits. What would he have concluded if he had observed a 3:1 ratiofor two traits

Mendel would have concluded that one pair of factors (genes) is responsible for two different characters in plants.

Explanation:

The 9:3:3:1  ratio observed by Mendel helped him to form his Law of Independent Assortment which states that the inheritance of one pair of factors (genes) is independent of the inheritance of the other pair.

Also from his previous studies, he obtained a 3:1 ratio for a single gene expression, flower color, which enabled to form the Law of Segregation, which states individuals possess two alleles and a parent passes only one allele to his/her offspring.

However, if he had observed a 3:1 ratio for two traits, he would have concluded that inheritance of characters occurs in pairs i.e., that a pair of alleles is responsible for two different characters in plants.