All protozoans are-

Options

A. Saprophytes only
B. Parasites only
C. Predators only
D. Heterotrophs (parasites or predator) only

Answer

**Step-by-Step Solution:**

1. **Understanding Protozoans**: Protozoans are unicellular organisms that belong to the kingdom Protista. They are classified as eukaryotes, meaning they have a defined nucleus and organelles.

2. **Nutritional Classification**: Protozoans are primarily heterotrophic. This means they cannot produce their own food through photosynthesis like plants. Instead, they obtain their nutrients by consuming other organisms.

3. **Types of Feeding**: While protozoans can exhibit different feeding behaviors, such as being predators (consuming other organisms) or parasites (living off a host), the question asks about all protozoans collectively.

4. **Conclusion**: Since all protozoans are heterotrophs, regardless of whether they are predators or parasites, the correct answer is that all protozoans are heterotrophs.

**Final Answer**: All protozoans are heterotrophs.

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