Two substances A and B when brought together form a substance C with the evolution of heat. The properties of C are entirely different from those of A and B. The substance C is

Options

A. a compound
B. an element
C. a mixture
D. none of these.

Explanation

To solve the question, we need to analyze the information provided about substances A and B and the resulting substance C. Here’s a step-by-step breakdown:

### Step 1: Identify the Reaction
The question states that two substances A and B, when combined, form a new substance C with the evolution of heat. This indicates a chemical reaction is taking place.

**Hint:** Look for clues that indicate a reaction, such as heat evolution or the formation of a new substance.

### Step 2: Understand the Properties of C
The properties of substance C are entirely different from those of substances A and B. This suggests that C is not just a mixture of A and B but a completely new substance with distinct characteristics.

**Hint:** Consider what it means for a substance to have different properties from its components.

### Step 3: Classify Substance C
Since C has different properties from A and B and is formed through a chemical reaction (as indicated by heat evolution), we can classify C as a compound. Compounds are formed when two or more elements chemically combine, resulting in a substance with properties different from those of the individual elements.

**Hint:** Remember the definition of a compound: it is formed from two or more elements that are chemically bonded.

### Step 4: Eliminate Other Options
- **Elements:** If C were an element, it would consist of only one type of atom, which contradicts the information given.
- **Mixture:** If C were a mixture, it would retain the properties of A and B, which is not the case here since C has entirely different properties.

**Hint:** Use the definitions of elements and mixtures to rule them out based on the properties of C.

### Conclusion
Based on the analysis, we conclude that substance C is a **compound** because it is formed from the chemical combination of substances A and B, resulting in a new substance with distinct properties.

**Final Answer:** The substance C is a compound.