The correct answer is D. a word root.
Chron is a Greek root which means time. So any word you make that contains this root will be related to time. For example: chronological, chronicle, chronometer, etc.
Homonyms are words that are written/read the same, but have different meanings (a Pole, as in a person from Poland, and a pole, as in a stick). A prefix is added before the root word (re-write). An adverbial suffix is added after the root word.
Chron is a root, which means that prefixes and suffixes are added to it.