HEXAM is WordPress plugin which lets you to provide online quizzes, mini-exams. Number of questions of each quizz and number of answers of each question you can set yourself. The plugin supports full html,css and has not rich default css, so you are free in building very different interface.
2. mTouch Quiz
This plugin also lets you to add quizzes to your site. But this plugin has ready interface, and question is given to user one by one.
3. WP Survey And Quiz Tool
Developer can create his own quiz, test, exam or survey.