Answer: Option A -- A longer stamen could ensure that an insect brushes against an another and picks up pollen
Step-by-step explanation:
A stamen is a particular structure in flower that produces pollen, which consists of anther and filament. Stamen are constructed in most flowers, not only to promote cross-pollination but also to avoid self-pollination. In addition, A longer stamen could ensure that an insect brushes against an another and picks up pollen.