How do you tell the difference between a subject and verb?

Read the excerpt from eighty years and more: reminiscences, 1815-1897. all that day and far into the night i pondered the problem of boyhood. i thought that the chief thing to be done in order to equal boys was to be learned and courageous. so i decided to study greek and learn to manage a horse. which question would best the reader understand stanton's viewpoint in this excerpt?