These two organisms may have evolved by coevolution. The last option in the given question is the correct option. The Latin-American humming birds had to evolve as per their surroundings, otherwise they would have become extinct in that region. For that sole purpose they had to have the long and curved bills. The flowers needed the humming birds for their pollination. To attach with the legs of the humming birds in the region, the flowers had to become sharply curved. The humming birds had to come in contact with the flower while sucking the nectar. this helped the plants in their pollination process. so both became mutually beneficial to each other.