Answer:C) 0%
Explanation: The probability of the an offspring bein white is 0%. A cross between a homozygous purple plant and a homozygous white plant will result in all the offsprings having a genotype of Pp. Purple (P) is dominant over white (p) which is recessive, therefore offsprings with a Pp genotype are heterozygous for purple color and will manifest outwardly as purple plants. Therefore none of the offsprings will be white.
See the attached punnett square for illustration.