If W = purple flower and w = white, and D = tall plants and d = short plants, a wwDd plant would be
purple and tall
purple and short
white and tall
white and short
As we have discussed in Dihybrid Cross -
As per this question, the homozygous recessive alleles (ww) would confer white color while the heterozygous alleles (Dd) would confer tall height to the plant. Hence, the phenotype would be white and tall.
Therefore, the correct option is (c).