The correct answer is option 3: pollination by air. Pollination is the process of transferring pollen from the male part of a flower to the female part, which is necessary for fertilization and seed production. In maize, also known as corn, pollination occurs by air. Maize is a wind-pollinated plant, meaning that it does not rely on insects or other animals for pollination. Maize flowers produce large amounts of pollen that is released into the air. The wind carries the pollen from the tassel, the male part of the flower, to the silks, the female part of the flower, allowing for fertilization to occur. This method of pollination is efficient for maize plants, as it enables the transfer of pollen over long distances.