You Are Studying a Genus of Tropical Plants Pollinated by Lowland

You are studying a genus of tropical plants pollinated by lowland birds. These plants grow in low density and are widely separated from one another. However, one species in the genus has adapted to high alpine meadows, where it is the most abundant plant over large areas. The alpine species has flowers that are small and dull, and unisexual. You infer that:

A) adaptation to an alpine environment required a shift from bird to wind pollination.
B) reproduction is more efficient in the alpine environment than in the lowland environment.
C) the alpine environment is likely nutrient poor, leading to small, dull flowers and poor pollination success.
D) the alpine species is most likely bee pollinated, because bee pollination is only efficient at high densities of individual plants.