The fit on a hole-shaft pair system is specified as H7-h6, which indicates the type of fit between the hole and shaft. In this case, the correct answer is option 'A', which represents a clearance fit. Let's break down the explanation to understand why this is the correct answer.

1. Understanding the Fit System:
- The fit on a hole-shaft pair system is used to define the tolerance and clearance between the hole and shaft. It ensures proper mating and functioning of the components.
- The fit system consists of a combination of a capital letter (such as H, G, F, etc.) representing the hole tolerance and a lowercase letter (such as h, g, f, etc.) representing the shaft tolerance.

2. H7 and h6 Tolerances:
- In the given fit system, H7 represents the hole tolerance and h6 represents the shaft tolerance.
- H7 is a hole tolerance that provides a relatively loose fit, allowing for a certain amount of clearance between the hole and shaft.
- h6 is a shaft tolerance that provides a relatively tight fit, ensuring a smaller amount of clearance between the shaft and hole.

3. Clearance Fit:
- A clearance fit is a type of fit where the maximum shaft size is always smaller than the minimum hole size. There is always a gap or clearance between the hole and shaft.
- The clearance allows for easy assembly and disassembly of the components without requiring much force.
- It also allows for relative motion between the components, such as sliding or rotating.

4. H7-h6 Fit:
- In the given fit system, H7 represents a hole tolerance that provides a relatively loose fit, while h6 represents a shaft tolerance that provides a relatively tight fit.
- Since the shaft tolerance (h6) is smaller than the hole tolerance (H7), it creates a clearance fit.
- This means that the maximum shaft size will always be smaller than the minimum hole size, allowing for a certain amount of clearance between the hole and shaft.

In conclusion, the fit specified as H7-h6 represents a clearance fit. This fit allows for easy assembly and disassembly of the components and provides a gap or clearance between the hole and shaft, allowing for relative motion.