Final answer:
The phenotypic ratio among the offspring of two heterozygous tall pea plants (Tt x Tt) is 3 tall to 1 dwarf.
Step-by-step explanation:
If tall (D) is dominant to dwarf (d), and two heterozygous parents are crossed, the ratio of phenotypes among the offspring can be predicted using a Punnett square. In such a cross, each parent has the genotype Tt, and the possible genotypes for their offspring are TT, Tt, Tt, and tt. This results in three possibilities for offspring to be tall (TT, Tt, Tt) and one possibility for offspring to be dwarf (tt). Therefore, the phenotypic ratio among the offspring is 3 tall : 1 dwarf.