Locate the quiz of your choice
Scroll down to the Quiz Administration Block
Select Edit Quiz.
After selecting “Add”, one has the option to manually type a question, select one from a question bank or add a random question.
NOTE: It is recommended that instructors have question banks to choose from or manually add a question. When one adds a random question, Moodle may or may not recognize the question if that question is not located in any of your question banks.