Final answer:
When reversing a school bus and losing sight of the guide, it is important to stop moving and become stationary until the guide passes. It is advisable to wait for assistance to ensure the safe reversal of the bus.
Step-by-step explanation:
When reversing a school bus and you lose sight of the guide, it is important to take necessary precautions to ensure safety. Firstly, you should stop moving and become stationary until the guide passes by. This will prevent any potential accidents or collisions. Secondly, it is advisable to wait for assistance from someone who can help guide you in reversing the bus safely. This could be another driver or a staff member who is familiar with the surroundings.