The partial Punnett square shows a cross between two tall pea plants. The allele for tall height (T) is dominant, and the allele for short height (t) is recessive. What fraction of offspring does the Punnett square predict will be tall?
A. Three-fourths
B. All
C. Half
D. None

Since neither the Punnett square nor genotypes of the tall plants have been given, tall phenotype could be homozygous (TT) or heterozygous (Tt). Therefore, the following ratios are possible:

If parents are TT X TT, B) All will be true as all plants will have TT genotype and tall phenotype.

If parents are TT X tt, B) All will be true as all plants will have Tt genotype and tall phenotype.

If parents are Tt X Tt, A) Three-fourths will be true as 3 plants will be tall (1TT, 2 Tt) and 1 will be short (tt).