Answer:
D. They attract birds and insects that aid in the pollination process.
Step-by-step explanation
Pollination is essential for the propagation of a plant.
Most pollinators fly, so a bright flower colour will attract them.
Flowers that bloom at night use odours to attract pollinators like moths and bats, which don't see colours.
A is wrong. The pollinators are after the nectar, not the plant.
B is wrong. The plant is not sentient.
C is wrong. A large herbivore isn't deterred by a flower's fragrance.