Answer:
The most appropriate answer would be option D.
The ratio of plants with a tall stem to plants with a short stem in roughly equals to 3:1, that is, the phenotype ratio is roughly equal to 3:1.
Thus, by Mendelian genetics, the ratio of the genotypes should be roughly equal to 1 (TT): 2 (Tt): 1 (tt).
Hence, about 50 percent of the population should be heterozygous in nature.