Yes. Your exam answers are automatically saved as you complete your exam. You are therefore able to pause at any time, whether it's to return to the course material or to step away from the course, and you can pick up where you left off when you return at a later time.
Note: You can only pause your exam as long as at least one question has not been answered. Once an answer has been selected for all questions, you will only be able to Submit your exam to be scored.