Predict the result
The source diagram places the set of terriers inside the universal set of dogs.
What relationship does it show?
Read the smaller region’s containment.

Set up the model
Every element of the smaller set belongs to the containing set.
That is the subset relationship.

Work the example
Use T for terriers and U for the diagram’s universal set of dogs.
Write T is a subset of U.
In words, every terrier in this diagram is a dog.
The circle’s location makes the inclusion visible.

Check the result
Now interpret the source diagram with lions inside cats.
Take eight seconds to think before the answer appears.
[Eight-second silent pause to work; the answer remains hidden.]
L is a subset of U.
Every lion in the diagram belongs to the set of cats.

Interpret the result
Read containment relative to the diagram’s stated universe.
Use the original task and check that your result fits its meaning.