Which of these is not a primary source? A. Diaries B. Letters C. Oral histories or D..text book?

Which of these is not a primary source

D. text book

i confess that there are several parts of this constitution which i do not at present approve, but i am not sure i shall never approve them: for having lived long, i have experienced many instances of being obliged by better information or fuller consideration, to change opinions even on important subjects, which i once thought right, but found to be otherwise. it is therefore that the older i grow, the more apt i am to doubt my own judgment, and to pay more respect to the judgment of others.

its many islands, high mountains, and remote peninsulas isolated population centers.