Question

A cross between two tall plants resulting in offsprings having few dwarfs

Answer 1

it is because, the two tall plants are now pure tall, the are heterozygous i.e. consists of Tt gene. and by the cross of these plants, we get 3 tall and one dwarf plant.

I hope it will help you

Answer 2

this means that the tall plants are not pure tall i.e. TT but it is impure tall i.e. Tt and crossing between Tt*Tt would give us 4 offsrings i.e. TT, Tt, Tt, tt