QuizSlides is a service whose purpose is to help you build quizzes based upon your slides. I've been using the service off and on since 2012. This week the QuizSlides developers sent out an email in which they explained that they can no longer support "a high volume of concurrent users" outside of their university. To that end QuizSlides will cease support for concurrent use on August 1st. But if you haven't logged into your account at all by March 31st your account will be closed.
If you have been using QuizSlides and still want to use it for training purposes in a setting in which you will not have a high volume of concurrent quiz takers, QuizSlides will still offer QuizSlides Training. Again, log into your account keep this option active.
QuizSlides allows you to upload PPT or PPTX files containing questions then add answer choices to create an instant-feedback quiz. The quiz can be set to allow students to try answers until they get the correct answer or the quiz can be set to allow only one try per question.