Based on this information, what is Petunia's phenotype for the wool color trait?

 - black wool
 - white wool
Petunia's genotype for the wool color gene is LL. Petunia's genotype of LL has only L allelles. The L allele is for white wool. So, Petunia's phenotype for the wool color trait must be white wool.
To check this answer, consider whether Petunia's alleles are dominant or recessive. The allele for black wool (l) is recessive to the allele for white wool (L). This means L is a dominant allele, and l is a recessive allele.
Petunia's genotype of LL has two dominant alleles. An organism with at least one dominant allele for a gene will have the dominant allele's version of the trait. So, Petunia's phenotype for the wool color trait must be white wool.