An obligate paraiste is one which

Options

A. always requires a living host
B. is normally a parasite but can become a saprophyte
C. always requires dead organic matter to live on
D. is usually a saprophyte but can become a parasite

Answer

### Step-by-Step Solution:

1. **Understanding the Term "Obligate Parasite":**
- An obligate parasite is defined as an organism that is entirely dependent on a living host for its survival and reproduction. This means that it cannot live or grow without a host.

2. **Distinction Between Obligate and Facultative Parasites:**
- It is important to differentiate between obligate parasites and facultative parasites. While obligate parasites must have a living host, facultative parasites can live independently or as parasites, depending on the environment.

3. **Nutritional Requirements of Parasites:**
- Parasites, including obligate parasites, obtain their nutrients from their host. They rely on the living tissues of their host organisms for sustenance.

4. **Examples of Obligate Parasites:**
- A classic example of an obligate parasite is *Plasmodium*, the genus of protozoa that causes malaria. This organism requires a living host (such as humans or mosquitoes) to complete its life cycle.

5. **Conclusion:**
- Based on the definitions and examples provided, the statement that best describes an obligate parasite is: "always requires a living host."

### Final Answer:
An obligate parasite is one which **always requires a living host**.

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