The shell of Nautilus is

Options

A. Bivalved
B. Spirally coiled
C. Multi-chambered
D. Both B and C

Answer

To answer the question "The shell of Nautilus is," we need to analyze the characteristics of the Nautilus shell based on the information provided.

### Step-by-Step Solution:

1. **Identify the Type of Shell**: The shell of Nautilus is not bivalve. Bivalve shells consist of two hinged parts, which is not the case for Nautilus. Instead, Nautilus has a single, spirally coiled shell.

**Hint**: Remember that bivalves have two shells, while Nautilus has one.

2. **Determine the Shape of the Shell**: The Nautilus shell is described as spirally coiled. This means that the shell has a spiral shape, similar to that of a snail.

**Hint**: Think about the shape of a snail's shell when considering the Nautilus shell.

3. **Examine the Structure of the Shell**: The Nautilus shell is also multi-chambered. This means that the shell is divided into several chambers, which help the animal regulate buoyancy and swim effectively.

**Hint**: Multi-chambered structures can be beneficial for buoyancy control in aquatic animals.

4. **Combine the Characteristics**: Given that the shell is spirally coiled and multi-chambered, we can conclude that the correct description of the Nautilus shell includes both of these features.

**Hint**: Look for options that include both spirally coiled and multi-chambered characteristics.

5. **Select the Correct Option**: From the options provided, the correct answer would be "both B and C," as these options correctly describe the Nautilus shell.

**Hint**: Always check if an option combines multiple correct characteristics when available.

### Conclusion:
The shell of Nautilus is spirally coiled and multi-chambered, making the correct answer "both B and C."