Animal welfare refers to respecting the rights of animals, protecting the ecological environment, and promoting the coordinated development of humans and animals. Animal welfare mainly includes: physical welfare, that is, no worry about hunger and thirst; environmental welfare, that is, allowing animals to have appropriate housing; health welfare, That is to minimize animal injuries; behavioral welfare, which guarantees the animal's natural freedom of expression; psychological welfare, which reduces the animal's fear and anxiety. Based on the above definition, which of the following does not involve animal welfare? ? ['Injecting narcotics into live animals for scientific purposes.', 'Take multiple rewards to motivate monkeys to perform difficult moves.', 'Reserve multiple animal crossing bridge culverts when constructing highways in mountainous areas.', 'Chicken farms allow hens to freely forage in mountain forests to increase egg production.']