Question

which area would you select to change the vertical space between lines of type?

Explanation:

In typography, the vertical space between lines of type is known as leading. In the given interface, the "Aa" (leading) option (highlighted with a red box in the image) is specifically used to adjust this vertical spacing.

Answer:

The area with the "Aa" label (showing "0 pt" in the image) is selected to change the vertical space between lines of type.