⟩ Which one of the following best describes a "user co-ordinate System"?
(a) The pair of co-ordinate points which define the lower left and upper
right corners of the drawing boundary
(b) A series of co-ordinate points stored as variables for later use in the
drawing
(c) A co-ordinate system whose origin is located anywhere in three
dimensional space
(d) The master datum from which all measurements are taken.