Which of the following statements regarding air is incorrect?

Options

A. Air contains dust particles and water vapour.
B. Air neither has fixed shape nor has fixed volume.
C. Air has mass and occupies space.
D. Air is incompressible.

Explanation

To determine which statement regarding air is incorrect, let's analyze each statement step by step.

### Step 1: Analyze the first statement
**Statement:** Air contains dust particles and water vapor.
**Analysis:** This statement is true. Air is a mixture of gases and can contain various impurities, including dust particles and water vapor.

### Step 2: Analyze the second statement
**Statement:** Air neither has fixed shape nor has fixed volume.
**Analysis:** This statement is also true. Air takes the shape of its container and can expand or compress, meaning it does not have a fixed shape or volume.

### Step 3: Analyze the third statement
**Statement:** Air has mass and occupies space.
**Analysis:** This statement is true as well. Air is made up of molecules that have mass, and it occupies space, which can be demonstrated by filling a balloon with air and weighing it.

### Step 4: Analyze the fourth statement
**Statement:** Air is incompressible.
**Analysis:** This statement is incorrect. Air is compressible, meaning it can be compressed into a smaller volume. This is due to the significant amount of space between air molecules, allowing them to be pushed closer together.

### Conclusion
Based on the analysis, the incorrect statement regarding air is: **"Air is incompressible."**

### Final Answer
The answer is: **Option 4: Air is incompressible.**

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