Which of the following is not a compound?

Options

A. sugar
B. common Salt
C. diamond
D. plaster of Paris

Explanation

To determine which of the following options is not a compound, we need to understand the definition of a compound and analyze each option based on that definition. A compound is a substance formed when two or more different elements are chemically bonded together.

### Step-by-Step Solution:

1. **Understand the Definition of a Compound**:
- A compound consists of two or more different elements that are chemically combined in a fixed ratio.

2. **Analyze Each Option**:
- **Sugar (Glucose)**: The chemical formula for glucose is C6H12O6. It consists of carbon (C), hydrogen (H), and oxygen (O). Since it contains more than one element, it is a compound.
- **Common Salt (Sodium Chloride)**: The chemical formula for common salt is NaCl. It is made up of sodium (Na) and chlorine (Cl), which means it also consists of more than one element, making it a compound.
- **Diamond**: Diamond is a form of carbon where each carbon atom is bonded to four other carbon atoms. Since it is made up of only one type of element (carbon), it is not a compound.
- **Plaster of Paris**: The chemical formula for Plaster of Paris is CaSO4·1/2H2O. It contains calcium (Ca), sulfur (S), and oxygen (O), indicating that it is made up of more than one element, thus it is a compound.

3. **Identify the Correct Answer**:
- Based on the analysis, diamond is the only substance that is not a compound because it consists solely of carbon atoms.

### Conclusion:
The substance that is not a compound among the given options is **Diamond**.