Question

If you want the reader to know what all of your characters are thinking, you must

have the narrator tell the story
use an omniscient narrator

Answer 1

Use an omniscient narrator.

Step-by-step explanation:

Google says, "Omniscient is a literary technique of writing a narrative in third person, in which the narrator knows the feelings and thoughts of every character in the story. ... Omniscient narrative tells the story of every character by demonstrating that only the narrator possesses information."

Hope it works for ya.