Which best identifies an element of an effective summary? a. the author's name must be included in the text of the paper. b. the author's tone must be changed. c. the author's ideas must be rephrased into your own words. d. the author's professional qualifications must be included.

The correct option is C.
An effective summary must have some features which include the following:
It must serves as a mean of getting a quick information about the content of the text. It must provide accurate and precise presentation of the original text most important points. It must be paraphrased to show the author's original thoughts.