In the past few years, we have covered plenty of awesome plugins that let you host online exams on your site. The Online Exam Management Plugin is also worth a look. It is a paid plugin that lets you create exams with various question types, set exam centers and duration, and manage students.
You can create any number of exams with this plugin. The Online Exam Management plugin supports single-choice, multiple choice, subjective, and objective questions. They can be randomized for each student. Users can view complete answer sheet for each student and import/export data in CSV format.
This plugin has a centralized start time for exams. Webmasters have the option to show results after the completion of each exam.