Final answer:
The correct answer is C, where both organisms involved in a symbiotic relationship benefit or are neutrally affected, which differs from parasitism where the parasite harms the host.
Step-by-step explanation:
In a symbiotic relationship, the correct answer is C. both organisms involved benefit or are neutrally affected. Unlike parasitism, where the parasite benefits at the expense of the host, symbiosis includes relationships such as mutualism, where both parties gain something, and commensalism, where one benefits without harming the other. The example provided of gut bacteria is a case of mutualism, as the bacteria help in digesting food and producing vitamins while receiving a habitat and nutrients. The bacteria help break down food and supply the host with vitamins it cannot produce on its own, while the host supplies the bacteria with food.