Langerhans' cells are white blood cells in the immune system that normally play an important role in protecting the body against viruses, bacteria and other invaders. They are found in the skin, lymph nodes, spleen, bone marrow and lungs.
I think it's letter A.litter left on the field after a ball game
You should expect an endangered species to be more SPECIALIST. Animal species that can live in different types of environment and which can survive on different types of food are called generalist. This type of animal specie can not be easily endangered because they have high level of survival. The specialist animal species on the other hand are adapted to a narrow range of food and environment. Specialist species can be easily wipe out if there food resources is exhausted or if their habitat is destroyed.