Write a question for: resposta com since, for e yet

Hello everybody!

I'm having some troubles in an exercise where I must write questions for sentences in the Present Perfect. I don't know exactly how to make a question for the sentences which use since, for and yet. Can you guys suggest me some questions? Here are the exercises:

1. ______________________________________
He has managed the restaurant since last semester.

2. ______________________________________
She hasn't ironed the shirts yet.

3. _______________________________________
She hasn't worn her sandals yet.

4. ________________________________________
They haven't knocked on the door yet.

Thanks in advance!