Question

what is the main purpose of a thought bubble in a graphic novel?
it displays authentic dialogue.
it illustrates internal dialogue.
it shows what the characters say.
it gives background information.

Explanation:

Thought bubbles in graphic novels are used to show the internal thoughts of characters. They are distinct from dialogue bubbles (which show what characters say) and other elements like background information - providing panels.

Answer:

It illustrates internal dialogue.