A group completely devoid of contractile vacuoles is

Options

A. Sporozoa
B. Sarcodina
C. Ciliata
D. Zooflagellata.

Answer

To answer the question "A group completely devoid of contractile vacuoles is," we need to analyze the different groups of protozoan protists based on their characteristics, particularly focusing on the presence or absence of contractile vacuoles.

### Step-by-Step Solution:

1. **Understand the Groups of Protozoan Protists**:
- Protozoan protists are classified based on their mode of locomotion into different groups such as Sporozona, Sarcodina, Ciliata, and Zooflagellata.

2. **Identify the Groups**:
- **Sporozona**: These organisms have a spore-like stage in their life cycle and lack locomotory organs. An example is Plasmodium vivax, which causes malaria.
- **Sarcodina (Rhizopoda)**: This group includes amoebas, which possess pseudopodia for movement and have contractile vacuoles.
- **Ciliata**: This group, represented by organisms like Paramecium, has cilia for movement and also contains contractile vacuoles.
- **Zooflagellata**: Organisms in this group, such as Trypanosoma gambiense (causative agent of sleeping sickness), have flagella for movement and possess contractile vacuoles.

3. **Analyze Each Group for Contractile Vacuoles**:
- **Sporozona**: No contractile vacuoles present.
- **Sarcodina**: Contractile vacuoles are present.
- **Ciliata**: Contractile vacuoles are present.
- **Zooflagellata**: Contractile vacuoles are present.

4. **Conclusion**:
- From the analysis, it is clear that the **Sporozona** group is the only one completely devoid of contractile vacuoles.

Thus, the answer to the question is **Sporozona**.