The alleles for tall height in pea plant is dominant over short height. why do you always know the genotype of a tall plant?

you know because if its a tall plant the genotype is dominant whereas if its short its recessive

hope this helps :)

You always get the genotype for the tall plant because the tall plant gene is dominant. The dominant will always show even if it is just one allele because the dominant always takes over the recessive allele