What is the maximum speed limit in a school zone when children are present?

Answer: B — 30 km/h

In most countries, the maximum speed limit in a school zone when children are present is 30 km/h. This is because children are at a higher risk for accidents and may not be able to react quickly to unexpected situations. Option A (20 km/h) would be too slow and could potentially cause traffic issues, while option C (40 km/h) and D (50 km/h) would be too fast and increase the likelihood of accidents. It is important to always be cautious and follow the designated speed limit in school zones to ensure the safety of children.