Dear Gail, thanks a lot for your question and sorry about our delay. The lesson above is about using the impersonal "se" + a verb in the 3rd person singular. However, if the verb is conjugated in the 3rd person plural, we are dealing not with an impersonal sentence, but with a passive sentence instead. Therefore, in the quiz you can find "se" followed by the 3rd person singular or plural depending on the context. I hope this explanation makes more sense to you and do not hesitate to contact us again if you need further help.