Random question type
From Learnit docs
Template:Questions A random question is not a question type as such, but is a way of inserting a randomly-chosen question from a specified category into a quiz.
This means that different students are likely to get a different selection of questions, and when a quiz allows multiple attempts then each attempt is likely to contain a new selection of questions.
You should always keep in mind that Moodle always adds random questions as worth 1 mark. See this forum thread.
See this forum thread for more details.