Which of the following is not characterised by cell wall?

Options

A. Animal
B. Blue-green algae
C. Mycoplasma
D. Plants

Explanation

To determine which of the following options is not characterized by a cell wall, we can analyze each option provided:

1. **Animals**: Animals do not have a cell wall. Instead, they are surrounded by a plasma membrane, which serves as the outer limiting structure. This is a key characteristic of animal cells.

2. **Blue-green algae (Cyanobacteria)**: Blue-green algae do have a cell wall. Their cell wall is primarily made of peptidoglycan, which is a common feature of many prokaryotic organisms.

3. **Mycoplasma**: Mycoplasma are a group of bacteria that are unique because they lack a cell wall. They have a plasma membrane but no rigid cell wall structure, making them distinct among bacteria.

4. **Plants**: Plant cells are characterized by having a cell wall made primarily of cellulose. This cell wall provides structure and support to the plant cells.

Based on this analysis, the correct answer to the question "Which of the following is not characterized by a cell wall?" is:

**Answer**: Animals

### Step-by-step Solution:
1. **Identify the options**: The options provided are animals, blue-green algae, mycoplasma, and plants.
2. **Analyze each option**:
- **Animals**: No cell wall, only a plasma membrane.
- **Blue-green algae**: Have a cell wall.
- **Mycoplasma**: Lack a cell wall, only have a plasma membrane.
- **Plants**: Have a cell wall made of cellulose.
3. **Determine which option does not have a cell wall**: Animals and mycoplasma do not have a cell wall, but since the question asks for the option that is not characterized by a cell wall, we focus on animals as the most common example.
4. **Conclude the answer**: The answer is animals, as they do not possess a cell wall.