The question involves understanding the concept of pH and how different substances interact with it. The pH scale measures the acidity or basicity of a solution. The scale ranges from 0 to 14, where values below 7 indicate acidic solutions, values above 7 indicate basic solutions, and a value of 7 is neutral.

Given that the soil mixed with water turns the pH paper yellowish orange, we infer that the solution is acidic. This is because pH paper turns yellow to orange in acidic environments.

To change the color of the pH paper to bluish, we need to introduce a basic substance. Basic substances typically have a pH greater than 7, and they turn pH paper to shades of blue or green.

Let’s analyze the given options to determine which one is basic:

1. Milk of magnesia: This substance is a suspension of magnesium hydroxide, which is a base. It typically has a pH around 10.5, making it basic and capable of turning pH paper bluish.
2. Lemon juice: Lemon juice contains citric acid, which makes it acidic, not capable of turning pH paper bluish.
3. Vinegar: Vinegar contains acetic acid, making it acidic and unable to change the pH paper to bluish.
4. Common salt (sodium chloride): Common salt is neutral when dissolved in water and does not affect the pH to an extent that it turns pH paper blue.

Conclusion: Among the given options, Milk of magnesia is the basic substance. It will change the pH paper color from yellowish orange to bluish because of its basic nature.