The correct answer is option 2 - rough and sticky. When flowers are pollinated by insects, their pollen grains are typically rough and sticky. This helps the pollen grains to adhere to the body of the insect as they come into contact with them while the insect is visiting the flower. The rough texture of the pollen grains allows them to attach easily to the insect`s body, while the stickiness helps to keep them in place. This enables the insects to transport the pollen grains from one flower to another, facilitating cross-pollination. Insects such as bees, butterflies, and flies are often attracted to flowers for their nectar, and in the process of obtaining the nectar, they inadvertently transfer the pollen grains from one flower to another, aiding in the fertilization process.