What weather is favorable?

Cross-pollination is often easily limited by environmental conditions, and there is no opportunity for pollination, such as windless wind-borne pollination, and there are not enough insects flying out of pollination because of strong wind or low temperature, which reduces the opportunity for pollination and fertilization and affects the yield of fruits and seeds. Sunflowers are insect-borne flowers, and rainy weather is not conducive to the spread of pollen, and there are no insects. Small winds are good for insects to fly. Low temperature is not suitable for insect activities.

So choose: C.