Reddit user [FrenchGuy83](https://www.reddit.com/user/FrenchGuy83) [recommended](https://redd.it/ty6ypf) chose no, as attending the Defence Preparation Day isn't really serving in, helping, or participating in a military unit:

> I checked 'No' because you didn't actually enroll or join a military unit that day - there's no military training of any sort. I saw it more like attending a job/career fair and learning more about your options should you decide to join the army.

Reddit user [rrrhao](https://www.reddit.com/user/rrrhao) [recommended](https://redd.it/ty6ypf) also recommend to be consistent across forms:

> Did you ever filed a I-485? If so, match the answer on the I485.

The [I-485 form](https://www.uscis.gov/sites/default/files/document/forms/i-485.pdf) ([mirror](https://web.archive.org/web/20220403172612/https://www.uscis.gov/sites/default/files/document/forms/i-485.pdf)) does have some similar questions on military involvement indeed:

[![enter image description here][1]][1]





  [1]: https://i.sstatic.net/yNWPr.png