Millipedes may be characterized as ( ). A: active predators B: venomous C: scavengers and detritivores D: monoecious E: viviparous

The following cases belong to polymorphosis（ ）. A: In the same season, there are two types of viviparous female aphids: wingless and winged. B: Long wing and short wing of brown planthopper C: Workers and soldiers in ant population. D: Females and males of stag beetles