Explanation:

- The mean proportion is the geometric mean of two numbers, not to be confused with simple averages. It's calculated as the square root of the product of two numbers.

- To find the geometric mean of 7 and 112:

- Multiply 7 and 112 \(= 784\).

- Take the square root of 784 \(= 28\).

- Correct Answer: Option 2 - 28

- Option 1 - 42: This value is incorrect. It seems to be derived from an incorrect calculation or misunderstanding.

- Option 3 - 21: This value is too low and doesn't fit the geometric mean calculation.

- Option 4 - 14: This value is much too low, similar to option 3, and incorrect.