Which is a natural colloidal?

Options

A. Sodium chloride
B. Urea
C. Cane sugar
D. Blood

Answer

To determine which of the given options is a natural colloidal, we need to understand what a colloid is and identify the nature of each option provided.

### Step-by-Step Solution:

1. **Understanding Colloids**:
- A colloid is a mixture where one substance is dispersed evenly throughout another. The particles in a colloid are larger than those in a solution but smaller than those in a suspension. Colloidal particles typically range from 1 nanometer to 1 micrometer in size.

2. **Analyzing the Options**:
- **Sodium Chloride (NaCl)**: This is a salt that, when dissolved in water, forms a true solution. It does not form a colloidal system.
- **Urea**: Urea is a small organic molecule that also dissolves in water to form a true solution, not a colloid.
- **Cane Sugar**: Similar to NaCl and urea, cane sugar dissolves in water to form a true solution and does not create a colloidal system.
- **Blood**: Blood is a complex fluid that contains various components, including cells (like red blood cells and white blood cells) and proteins suspended in plasma. This makes blood a natural colloid.

3. **Conclusion**:
- Among the options provided, **blood** is the only natural colloidal substance. The other options (sodium chloride, urea, and cane sugar) are all examples of substances that form true solutions when dissolved in water.

### Final Answer:
**Blood is a natural colloidal.**

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