Complex characters are best described as

a. one-dimensional
b. predictable
c. realistic

Complex characters are best described as realistics. They are usually known for having complicated lives and histories, and sometimes their desires can even feel contradictory, as it occurs to real people.

Complex character are also called round characters in opposition to flat characters and they tend to be multi-dimensional characters.

Protagonists are often round characters just because readers know a lot about them, but any character in a story can be round.

  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.