Safety glasses must be worn by backhoe operators regardless of the cab windows being open or closed.

The correct answer is based on the principle of personal protective equipment (PPE) adherence in construction environments. Safety glasses are crucial for protecting the eyes from potential hazards, such as debris, dust, and other flying objects that may be encountered during operation.

In the context of backhoe operation, even when cab windows are closed, there can still be risks of flying particles or materials entering the cab area, especially when the machine is in motion or working in proximity to other activities. Open windows further increase this risk, as debris can more easily enter the operator's space. Therefore, regardless of the open or closed status of cab windows, wearing safety glasses remains a necessary precaution for all operators to ensure eye safety.

This understanding is essential in promoting a culture of safety, where precautions are emphasized at all times, not just when specific conditions are present. Hence, the requirement for safety glasses applies universally, supporting the notion that one should always be prepared for potential hazards in the surrounding work environment.