Define the macro switch, which takes in an expression expr and a list of pairs, cases, where the first element of the pair is some value and the second element is a single expression. switch will evaluate the expression contained in the list of cases that corresponds to the value that expr evaluates to.

While inserting images, the picture command is usually used to insert photos from a digital camera, and the clip art command is usually used to a.edit the sizes and other characteristics of photos that have been inserted. b.take a screenshot of an image and copy it to the clipboard for pasting. c.search for drawings or other images from a library of prepared pictures. d.make illustrations using lines and shapes that are easy to manipulate.