Answer: D) change the comma after “parts” to a colon.
Explanation: One of the most common uses of a colon is to introduce a list of elements (that will be separated with commas). From the given options, the one that expresses the revision that is necessary in the given sentence, is the corresponding to option D: change the comma after “parts” to a colon, so the correct sentence would be: Digestion is divided into four parts: ingestion, digestion, absorption, and elimination.
