Final answer:
The possible phenotypic ratio of offspring in a cross between a purple-flowered and a white-flowered pea plant is 100% purple.
Step-by-step explanation:
In this cross between a purple-flowered (PP) and a white-flowered pea plant (pp), the possible genotypes of the offspring will be Pp, which is heterozygous for flower color.
Since purple flowers (P) are dominant to white flowers (p), the phenotypic ratio of the offspring will be 100% purple.
Therefore, the correct answer would be Option A, 100% purple.