Pheromones are generally produced by

The correct answer is (d). Pheromones are generally produced by insects. They are chemical signals that are used to communicate with other members of the same species. Pheromones can be used for a variety of purposes, such as attracting mates, marking territory, and warning of danger.

Snakes, birds, and bats do not produce pheromones. Snakes use their tongues to sense pheromones that are produced by other snakes. Birds use their songs to communicate with each other. Bats use echolocation to navigate and find food.

Pheromones are a fascinating and important part of the natural world. They play a vital role in the communication and reproduction of many species.