Final answer:
The odd one out among the given options is radiation, as it is not a process of taking in substances.
Step-by-step explanation:
The odd one out among the given options is D. radiation.
Ingestion, absorption, and inhalation are all processes related to the intake of substances, while radiation is not a process of taking in substances but rather a form of energy transfer.
For example, ingestion is the process of taking in food through the mouth, absorption is the process of substances being taken into the bloodstream or cells, and inhalation is the process of breathing in air or gases.