The “3 dominant: 1 recessive” phenotypic ratio or “1 homozygous dominant :2 heterozygous dominant: 1 homozygous recessive” genotypic ratio is obtained by self pollination of F1 monohybrid. Thus, both parents are heterozygous tall (Tt). The presence of one homozygous parent would given the monohybrid test cross ratio of 1:1. Homozygous varieties produce uniform F1 generation of dominant or recessive individuals depending upon the genotype of homozygous parent. Thus, the correct answer is option C.