Explanation:

- Mean proportion refers to the geometric mean between two numbers. It is found using the square root of their product.

- The numbers given are 7 and 112.

- To find the mean proportion:

- Multiply 7 by 112 to get 784.

- Take the square root of 784.

- The square root of 784 is 28.

- Option:1, 42

- This is incorrect.

- Option:2, 28

- This is correct.

- The mean proportion between 7 and 112 is indeed 28.

- Option:3, 21

- This is incorrect.

- Option:4, 14

- This is incorrect.