to determine a waves' frequency, you must know the

a. distance it travels.
b. number of oscillations in a given period of time.
c. distance between the crest and trough.
d. height of the wave.

In windows explorer, select the file, folder, or groups of files and folders you'd like to copy. you can select multiple files or folders in several ways: click the first file or folder you want to select, hold down the ctrl key, and then click each additional file or folder you want.

An active cell. a circular reference occurs when a cell in an excel 2010 worksheet refers to itself.