Paragraph 1 establishes I. ethos
II. pathos
III. logos
A.
I
B.
II
C.
III
D.
I and II
E.
I, II, and III

Pathos and logos

Explanation:

Pathos is the appeal to emotions and logos is appeal to logic.

  this riddles' answer is library.

  the "leaves" are a reference to the books' pages that the library contains; the branches are a network of libraries that connect multiple libraries' collections, resources, and items in a system of a common database, integrating them; the branches' organization are a useful management tool for coordinating the multiple collections many libraries have.