Earn from paid subscription
You can create paid group.
user have to pay online to register for paid group. Further you can assign quiz into multiple group.
It support paypal, 2checkout, payumoney and paytm payment gateway.You just need to add APIs and its start working with app.
Advertisement code or banner
Earn from adsense or advertisement by showing ad on various locations. eg. header, footer, result page and even in between quiz (an ad banner will popup for few seconds).