Correct Response: C. The production of flowers and seeds requires relatively large amounts of energy, and after the shrub and tree leaf canopy has developed in the summer, the amount of sunlight on the forest floor is greatly reduced. Thus there is a strong energetic advantage to reproduce before the leaf canopy develops. Temperatures are higher during the summer (A), but these do not provide the energy required for reproduction. Fewer pollinators are active during the spring (B), and although there are fewer insect herbivores in the spring (D), this is not the primary reason for the frequency of early spring-blooming forest floor flowers.