What condition indicates Karel has reached the boundary of its world?

The condition that indicates Karel has reached the boundary of its world is when one of the wall checking functions returns true. In Karel's environment, these wall checking functions are specifically designed to determine if Karel has encountered a wall or an edge of the world. This functionality is crucial for safe navigation, allowing Karel to avoid moving into an area where it cannot proceed, which would typically lead to errors or unexpected behavior.

The wall checking functions are an integral part of Karel's ability to explore its environment, helping it recognize the limits of its operational space. When any of these functions return true, it's a clear signal that Karel cannot move in that direction anymore, as it has encountered a wall or a boundary.

The other options do not indicate that Karel has hit a boundary. Collecting all the beepers refers to completing a specific task rather than indicating physical limits. Moving a set number of steps does not inherently mean Karel has reached a boundary; it could still be moving within its world. Similarly, turning in a complete circle does not provide information on the presence of walls or boundaries.