Final answer:
In epithelial transport, the movement of substances from the internal to the external environment is called secretion, and from the external to the internal environment is called absorption; these processes involve exocytosis and endocytosis, respectively.
Step-by-step explanation:
In epithelial transport, movement from the internal environment to the external environment is called secretion, whereas movement from the external environment to the internal environment is called absorption. Therefore, the correct answer is E) secretion : absorption. Secretion involves the process of exocytosis, where cells export material using vesicular transport by fusing vesicles with the plasma membrane, allowing the contents to be released outside of the cell. On the other hand, absorption pertains to endocytosis, where the cell membrane engulfs a substance from the outside, forming a vesicle that brings the substance into the cell. Both endocytosis and exocytosis are examples of active transport processes, which are crucial for maintaining homeostasis and facilitating cellular functions.