TOEFL Listening: ETS-TOEFL听力机经 - 5NXXJ30O4886LCZ0P$

What does the professor imply when she discusses the fact that some violets periodically shift the positions of their petals? A. Violet petals shift to allow the widest possible dispersal of seeds B. Violets evolved to protect their nectar from being dried out by excessive sunlight. C. Various types of insects pollinate violets at different points in the flowering season. D. Petals on violets with the longest stalks shift position most dramatically.