What is dis number 19 what tool is it?

Mucous membranes.. a. cover or line external surface of body. b. line internal body surfaces that are in contact with the environment. c. produce antibodies to combat infection. d. secrete sweat, which has antibacterial enzymes.

Why is important to cover your hands and feet in cold weather? a. they are furthest from your heart. b. they are often last to receive blood flow. c. they can suffer from tissue damage in cold weather. d. all of the above

Waste is deposited into in thin layers which are then compacted and covered with soil.