Body cavity is the cavity present between body wall and gut wall. In some animals the body cavity is not lined by mesoderm.Such animals are called

Options

A. acoelomate
B. pseudocoelomate
C. coelomate
D. haemocoelomate

Explanation

To solve the question, we need to understand the classification of animals based on their body cavities. Here's a step-by-step breakdown:

### Step-by-Step Solution:

1. **Understand Body Cavity**: The body cavity is the space between the body wall and the gut wall. It can be classified based on its presence and the type of lining it has.

2. **Identify Types of Body Cavities**:
- **Acoelomates**: These animals do not have a body cavity (coelom) at all.
- **Coelomates**: These animals have a body cavity that is completely lined by mesoderm.
- **Pseudocoelomates**: These animals have a body cavity (pseudocoelom) that is not lined by mesoderm.

3. **Focus on the Question**: The question specifically asks for animals whose body cavity is not lined by mesoderm. This directly points to the term "pseudocoelomates".

4. **Conclusion**: Therefore, the correct answer to the question is that animals with a body cavity not lined by mesoderm are called **Pseudocoelomates**.

### Final Answer:
**Pseudocoelomates**

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