Key signatures tell is which key (which flats and sharps) to preform in and where "__" is located.

Perspective is important because it enabled the 3 dimensional world to be translated into the 2d world of the picture plane. this had an immediate impact on the representation of reality in art and design. 

The "maple leaf rag" (copyright registered on september 18, 1899)[1] is an early ragtime musical composition for piano composed by scott joplin. it was one of joplin's early works, and became the model for ragtime compositions by subsequent composers. it is one of the most famous of all ragtime pieces.[2] as a result joplin was called the "king of ragtime". the piece gave joplin a steady if unspectacular income for the rest of his life.

D. exterior reflects the interior, : )