In the skin, the epidermis can be compared to which of the following?
a wall that protects a country from invaders
a ship that transports cargo
a telephone line used to communicate information
a switch that turns a light on

A wall that protects a country from invaders

Explanation:

white blood cells or wbc s are mainly 2 types-

1.agranulocytes

2.granulocytes

the monocytes or macrophages of agranulocytes , dendritic cells which are accessory leucocytes, and b cells which is one type of lymphocytes   identify the antigens present on the pathogen's surface. these three cells are called antigen presenting cells(apc) which are phagocytes and destroy the antigens by secreting antitoxins. besides this leukocyte is always plays vital role in the immunity of the body.

oak trees? ? what was listed