The correct option is B. saprophyte. Explanation of the Correct Answer 1. Definition of Saprophyte: - A saprophyte is an organism that feeds on dead or decaying organic matter. These organisms play a crucial role in the ecosystem by breaking down complex organic materials, recycling nutrients back into the soil, and facilitating the growth of new plants. 2. Rhizopus and Mucor: - Rhizopus and Mucor are types of fungi that belong to the group known as zygomycetes. They are commonly found in soil, decaying fruits, and other organic materials. These fungi secrete enzymes that break down complex organic substances into simpler compounds, which they then absorb for nutrition. 3. Extracellular Digestion: - The term "extracellular" refers to the process of digestion occurring outside the organism's cells. In the case of Rhizopus, it releases digestive enzymes into the surrounding environment, breaking down the organic matter into smaller molecules that can be absorbed. This is a characteristic feature of saprophytic organisms. Why the Other Options are Incorrect A. A. a facultative parasite: - A facultative parasite is an organism that can live both as a parasite and as a saprophyte. While some fungi can exhibit this behavior, Rhizopus primarily feeds on dead organic matter and does not typically act as a parasite. Therefore, this option is incorrect. C. C. an obligate parasite: - An obligate parasite is an organism that can only live and reproduce by feeding on a host organism. This is not applicable to Rhizopus, as it does not require a living host to obtain nutrients. Instead, it thrives on decaying matter, making this option incorrect. D. D. a commensal: - A commensal organism lives in or on another organism without causing harm or benefiting the host. Rhizopus does not fit this definition, as it does not rely on a living host for sustenance. Instead, it actively decomposes dead organic matter, which is a different ecological role. Thus, this option is also incorrect. Summary of Key Points

• Saprophytes are organisms that obtain nutrients from dead organic matter, playing a vital role in nutrient cycling.
• Rhizopus and Mucor are examples of saprophytic fungi that utilize extracellular digestion to break down organic materials.
• The other options (facultative parasite, obligate parasite, commensal) do not accurately describe the feeding behavior of Rhizopus, as they imply a relationship with living hosts, which is not the case here.

Revision Summary

• Saprophytes feed on dead organic matter and recycle nutrients.
• Rhizopus and Mucor are saprophytic fungi that digest food extracellularly.
• Incorrect options involve relationships with living hosts, which do not apply to these fungi.
• Understanding the ecological roles of organisms helps clarify their classification and feeding strategies.