Contractile vacule to pump out excess of water is found in

Options

A. a) Fresh water protozoans
B. b) marine protozoans
C. c) Parasitic protozoans
D. d) Lower chordates

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks about the presence of contractile vacuoles, which are organelles that help in the regulation of water within certain organisms.

2. **Identifying the Function of Contractile Vacuoles**: Contractile vacuoles are responsible for collecting excess water from the cytoplasm of the cell and expelling it to the external environment. This is crucial for maintaining osmotic balance, especially in freshwater organisms.

3. **Analyzing the Options**:
- **Option A: Freshwater Protozoans**: These organisms live in environments where water is abundant. They tend to absorb water through their cell membranes, and thus, they need contractile vacuoles to expel the excess water.
- **Option B: Marine Protozoans**: These organisms are in saltwater environments where they face the opposite problem; they tend to lose water to their surroundings and do not require contractile vacuoles.
- **Option C: Parasitic Protozoans**: These organisms live within a host and often do not need to regulate water in the same way as free-living protozoans.
- **Option D: Lower Chordates**: While some chordates may have mechanisms for osmoregulation, they do not typically use contractile vacuoles.

4. **Conclusion**: Based on the analysis, contractile vacuoles are primarily found in freshwater protozoans, as they need to expel excess water to maintain osmotic balance.

5. **Final Answer**: Therefore, the correct answer is **Option A: Freshwater Protozoans**.