A great change has come . . . . . . . the world since the war.

The correct answer is: in.

The preposition “in” is used to indicate a location or position within something. In this case, the world is the location, and the change is the position. The change has come within the world, not outside of it.

The other options are incorrect because they do not indicate a location or position within something. The preposition “about” is used to indicate a topic or subject. The preposition “over” is used to indicate a position above or on top of something. The preposition “into” is used to indicate a movement or change into something.

Here are some examples of how the preposition “in” is used:

• The change has come in the world since the war.
• The change has come in the economy since the recession.
• The change has come in the way we live our lives since the pandemic.

I hope this helps! Let me know if you have any other questions.