In three kingdom classification, the kingdom Protista includes
(a) Unicellular eukaryotic organisms only
(b) Unicellular prokaryotic organisms only
(c) Wide variety of unicellular, mostly aquatic eukaryotes
(d) Wide variety of unicellular, mostly terrestrial Prokaryotes

Options

A. Unicellular eukaryotic organisms only
B. Unicellular prokaryotic organisms only
C. Wide variety of unicellular, mostly aquatic eukaryotes
D. Wide variety of unicellular, mostly terrestrial Prokaryotes

Answer

**Step-by-Step Solution:**

1. **Understanding Three Kingdom Classification**: The three kingdom classification system was proposed by Ernst Haeckel and includes three main groups: Plantae, Animalia, and Protista.

2. **Defining Kingdom Protista**: The kingdom Protista is primarily composed of unicellular organisms. These organisms are eukaryotic, meaning they have a defined nucleus and organelles.

3. **Nutritional Modes in Protista**: Organisms in the Protista kingdom can exhibit various modes of nutrition. They can be autotrophic (producing their own food), heterotrophic (obtaining food from other sources), or mixotrophic (capable of both).

4. **Analyzing the Options**:
- (a) Unicellular eukaryotic organisms only: This is true as Protista includes unicellular eukaryotes.
- (b) Unicellular prokaryotic organisms only: This is incorrect since Protista consists of eukaryotic organisms, not prokaryotic.
- (c) Wide variety of unicellular, mostly aquatic eukaryotes: This is also true, but it is more specific than option (a).
- (d) Wide variety of unicellular, mostly terrestrial prokaryotes: This is incorrect as Protista does not include prokaryotes.

5. **Conclusion**: The best answer that encompasses the characteristics of the kingdom Protista is option (c) "Wide variety of unicellular, mostly aquatic eukaryotes," as it highlights the diversity and aquatic nature of many protists.

**Final Answer**: (c) Wide variety of unicellular, mostly aquatic eukaryotes.

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