A candidate answers all ordinary PPSP topics well but answers an intersection-yielding question incorrectly. Why is this a special risk under HAK's PPSP criteria?

1. HAK states that a wrong answer on a question about yielding vehicles at an intersection can still mean the candidate did not pass, even above 90%
2. Intersection questions are optional and never scored
3. HAK scores all questions exactly one point, so one question cannot matter
4. Only first-aid questions can cause automatic failure