Final answer:
Mutualism in biology is a symbiotic relationship in which both species benefit.
Step-by-step explanation:
Mutualism in biology refers to a symbiotic relationship between two species in which both species benefit. This type of interaction requires reciprocal benefits between the interacting species, as stated in option B.
Examples of mutualism include the relationship between bees and flowers, where bees obtain nectar and flowers are pollinated, and the relationship between bacteria in the human gut and the host, where bacteria digest food and the host receives nutrients.