What command would you run to check if the next space is free before moving?

The command that should be used to check if the next space is free before moving is the one that employs the method frontIsClear(). This method specifically checks if there is an obstacle directly in front of Karel. If the path is clear, the move command will execute, allowing Karel to advance to the next space safely.

Using frontIsClear() is crucial for ensuring that Karel does not attempt to move into a space that is blocked, which would result in an error or unintended behavior in the program. It effectively allows a conditional approach, ensuring Karel only moves when it is safe to do so.

The other options may refer to different methods or contexts that do not directly verify the clearance in front of Karel specifically or may use incorrect terminology that does not align with the Karel programming environment. While they might seem reasonable in other contexts, they do not address the need for a clear path directly ahead of Karel before executing a move command.