Answer: C. It was heterozygous for both genes.
Explanation: To produce a generation that has individuals with trait for colored aleurone in the kernels, the plant being analised has to have a dominant allele R. In the same way, to have offspring with the recessive trait, it has to carry the recessive allele r. So, the unknown plant has to be heterozygous for colored aleurone in the kernels, Rr.
The same thought can be applied to plant color: Since there are green and yellow plants, the unknown plant has to be heterozygous for that trait, Yy.
In conclusion, the unknown plant is heterozygous for both genes.