There are no web services for this because no-one has ever needed them enough to implement them.
Opaque is the answer to a different question.
Quiz
Web Services To Access Moodle Questions
ការពិភាក្សាត្រូវបានបិទ ដូច្នេះអ្នកមិនអាចឆ្លើយតបទៀតទេ។