why is the progeny always tall when a tall pea plant is crossed with a short pea plant?
Yes exactly, your friends are right.
The gene for Tallness is dominant over the gene for dwarfness. So in the presence of the dominant gene the gene for dwarfness does not express itself.
The gene for Tallness is dominant over the gene for dwarfness. So in the presence of the dominant gene the gene for dwarfness does not express itself.