At the age of 21, Albert einstiens secured a job and as part of his job, he had to?

at the age of 21, albert einstein was a university graduate and unemployed.

Explanation:

(4) "oh, i've got better plans than that," laughed kerry. "i've got four firecrackers and two model rockets. care to join me in the backyard? "

this is the correct answer because of one simple word. "backyard"

  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.