It cannot be seen, it weighs nothing but when put in a barrel it makes it lighter, what is it?

  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.

a,b,c,d,e

explanation:

it would be nice to see the passage but with my understanding of the word oxymoron they speaker is saying that love is contradictory.