The authors statement that instances are by no means uncommon (paragraph 2, sentence 4) contributes to a tone that is

  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.

i will get back to you let me as my teacher

the statement that identifies the central idea of "the salem and other witch trail hunts" is d. while witch hunts may feel like a rare occurrence, mike kubic proves that such   incidents are not as uncommon as we originally thought.

the author is trying to show that witch hunts come in various forms and are produced by the fear of what isn't understood or it's different.