El brazo
Why?
A) El libro = The book, we need books in school so this is a school supply.
B) El lápiz = The pencil, we need pencils to write in on things so this is a school supply
D) La hoja de papel = A sheet of paper, we often write notes on paper so this is a school supply.
Finally, C) El brazo is an arm, this is a body part, not a school supply.
This is how we know the correct answer, which is not a school supply, is C) El brazo.
Hope this helps!~
