What do the prefixes 'in-' and 'non-' signify?

The prefixes 'in-' and 'non-' signify the meaning "not." When added to the beginning of a word, these prefixes change the word to indicate negation or the absence of something. For example, the word "incomplete" means not complete, and "nonfiction" means not fiction. This negating function is what these prefixes share, which is why the answer is correct. Understanding prefixes can help in deciphering the meanings of words and improving vocabulary.