Final answer:
Ladders should extend at least three feet above the level they serve for safety.
Step-by-step explanation:
According to ladder safety regulations, ladders should extend at least three feet above the level they serve. This provides a secure handhold on the ladder and helps prevent falls. It also ensures that the ladder is tall enough to safely reach the desired height. For example, if you need to access a roof that is 10 feet high, the ladder should extend at least 13 feet above the ground.