In this scenario, if half of the offspring are tall and half are short, it suggests that tallness is a dominant trait and shortness is a recessive trait. We typically designate the dominant allele with a capital letter and the recessive allele with a lowercase letter.
Since the tall pea plant contributes the dominant trait and the short plant contributes the recessive trait:
- The allele for tallness (dominant) would be designated as T.
Thus, the correct response is T.