Question

Which of the following is the commonly accepted form?

Were you born in the 1990's or 2000's?
Were you born in the 1990s or 2000's?
Were you born in the 1990s or 2000s?

Answer 1

It depends off opinion but definitely not the middle one. Having no idea what was said in the class I would go with the last option as it appears more often.

Answer 2

The last option tends to be the more accepted form.