| Answer | Crossword Clue |
|---|---|
| OBLIGATORY | Not optional |
| NEEDED | Not optional |
| IMPERATIVE | Not optional |
| ESSENTIAL | Not optional |
| NECESSARY | Not optional |
| REQ | Not optional: abbr. |
| REQD | Not optional: Abbr. |
| REQ | Not optional: Abbr. |
| NEED | It's not optional |
| MUSTS | They're not optional |
| NEEDS | They're not optional |
| MUST | It's not optional |
| AMUST | Something that's not optional |
| permissive | Allowed but not obligatory; optional |
