Based on this information, what is this plant's phenotype for the flower color trait?

 - light yellow flowers
 - dark yellow flowers
The rose plant's genotype for the flower color gene is ff. The rose plant's genotype of ff has only f alleles. The f allele is for dark yellow flowers. So, the rose plant's phenotype for the flower color trait must be dark yellow flowers.
To check this answer, consider whether the rose plant's alleles are dominant or recessive. The allele for dark yellow flowers (f) is recessive to the allele for light yellow flowers (F). This means F is a dominant allele, and f is a recessive allele.
The rose plant's genotype of ff has only recessive alleles. An organism with only recessive alleles for a gene will have the recessive allele's version of the trait. So, the rose plant's phenotype for the flower color trait must be dark yellow flowers.