Answer:
A. All are tall and purple
Step-by-step explanation:
When you set up a punnet square, all of the results would be TtPp.
When a dominant trait is present, it preceeds over the recessive trait. (Also it depends on what genotypes are given. Ex: In flowers if they gave RR shows red, Rw shows pink, and ww shows white, but that's not the case here given that there are only 2 genotypes).
So to break it down:
Tt -> tall plant
Pp -> purple plant
so they are all tall and purple.