Ontario Building Code Practice Exam

The minimum height required for a guardrail on a stairway landing in a residential building is 750 mm. This provides sufficient protection for individuals using the stairs. Option B, C, and D are incorrect because they are all higher than the minimum requirement and may be considered excessive. If the guardrail is too high, it may be difficult for individuals to use it for support or grab onto in case of a fall. Additionally, a higher guardrail may also obstruct the view of the stairway, which can be a safety hazard. Therefore, option A is the best answer as it meets the minimum requirement for safety while still being practical for use on a stairway landing.