The correct answer is D. Bees are a biotic factor that positively affects flower populations.
Step-by-step explanation
Biotic and abiotic factors are the living (biotic) and non-living (abiotic) physical and chemical components in ecosystems. These two influence the survival and reproduction of ecosystems. Therefore, bees are a biotic factor that affects the population of another biotic being (flowers). So the correct answer is D. Bees are a biotic factor that positively affects flower populations.