The correct option is
B a- Tall Red, b- Tall White, c- Tall Red, d- Dwarf Red
a is formed as a result of crossing TR and Tr.
That is : TTRr (Tall red)
b is formed as a result of Tr X Tr
That is: TTrr (Tall white)
c is formed as a result of tR X TR
That is: TtRR (Tall red)
d is formed as a result of tR X tR
That is : ttRR (Dwarf red)