Explanation:

- The sentence involves the submission of a school leaving certificate, which is a document associated with a specific individual.

- Option 1: "hers" - Indicates possession belonging to a female, but doesn't match the context, unless referring specifically to a female’s certificate.

- Option 2: "yours" - A possessive pronoun suggesting that the certificate belongs to the person being addressed, fitting if addressing the reader or listener directly.

- Option 3: "theirs" - A plural possessive pronoun, inappropriate here unless referring to multiple people's certificates collectively.

- Option 4: "your" - A possessive adjective correctly used to describe something belonging to the person being spoken to, fitting if it's one person's certificate.