The correct answers are unhappy, reread, restless, and comfortable.
An affix is a term which refers to suffixes (parts of words added at the end) and prefixes (parts of words added at the beginning). So, if you take a look at the words above, you will see that unhappy has a prefix un-, reread has a prefix re-, restless has a suffix -less, and comfortable has a suffix -able.
The other options do not have affixes.