Concept:An ecological relationship normally indicates an interaction between two organisms, whereas saprophytism is a single organism's mode of nutrition.
Explanation:Commensalism is a relationship in which one organism benefits while the other is neither helped nor harmed.
Symbiosis is the close association of two different organisms living together.
Parasitism is a relationship in which one organism, called the parasite, lives on or inside another organism, called the host, and obtains nourishment from it.
In all three cases, two organisms are clearly involved.
Saprophytism, however, is the process by which certain organisms feed on dead and decaying organic materials.
It only explains how a saprophyte obtains its food and does not describe a partnership or interaction between two organisms.
Therefore, saprophytism does not involve two organisms.
Answer:B. Saprophitism