The element of music defined as the ordered flow of music through time, or more specifically, the particular arrangement of note lengths in a piece of music, is: a) beat. b) meter. c) rhythm. d) tempo.

c) rhythm

Explanation:

Rhythm (to flow) is the positioning of sounds in time.

It is the one indispensable element in music. It is a measured motion (I.e a pattern) of strong and weak elements (contrasting elements) in the flow of sound (music).