Answer:
The similarities and differences between two ideas.
Explanation:
A Venn diagram is used to show all the possible relationships that are logical between a finite number of different sets.
Now lets look at each option and decide whether it can be represented with a Venn diagram or not.
"How much money has been spent in a monthly budget"
There are no different sets here.
"What you want to know about a subject"
There are no different sets here. If there were at least 2 subjects we could have drawn a Venn diagram.
"The similarities and differences between two ideas"
There are 2 different sets as ideas and we can make logical relationships between those 2 sets by using similarities and differences. So a Venn diagram can track this.
"The time order of a series of steps or events"
This should be represented using a timeline.