[Grammar] without adult's supervision

[Oceanlike]

I don't know if I should use an apostrophe mark in the following sentence.

- They should not be allowed to do that without adult's (adult) supervision.

If I don't use an apostrophe mark, is it incorrect? If it is okay to leave out the apostrophe, what's the reason?

Thank you.

 

[bhaisahab]

No possessive apostrophe. In 'without adult supervision' 'adult' is an adjective describing the type of supervision.