| Answer | Crossword Clue |
|---|---|
| OPTIN | Decide to join, e.g. |
| ENLIST | Join the Navy, e.g. |
| VOLUNTEER | Join the Peace Corps, e.g. |
| OPTIN | Decide to join |
| OPTOUT | Decide not to join in |
| SERBIA | 2009 applicant to join the E.U. |
| EDU | E-mail suffix once required to join Facebook |
