A symbiotic relationship in which one organism is completely dependent on another organism is called...

Explanation

In Biology, organisms often have relationships with each other, and one such relationship is called symbiosis. Symbiosis is a relationship in which two or more organisms closely interact with each other. One type of symbiotic relationship is called parasitism. In parasitism, one organism benefits at the expense of the other organism, which is harmed. In this relationship, the organism that benefits is called the parasite, and the organism that is harmed is called the host. In the context of the question, a symbiotic relationship in which one organism is completely dependent on another organism is called parasitism. This means that the dependent organism, the parasite, cannot live without the other organism, the host. The host provides the parasite with food and shelter, while the parasite harms the host. The other options listed in the question are commensalism, mutualism, saprophytism, and competition. Commensalism is a type of symbiotic relationship where one organism benefits and the other is neither helped nor harmed. Mutualism is a symbiotic relationship where both organisms benefit. Saprophytism is a relationship where one organism feeds on dead or decaying matter. Competition is a relationship where two organisms compete for the same resources. Therefore, the correct answer to the question is option A: Parasitism.