*Question T0B03:
Under what circumstances is it safe to climb a tower without a helper or observer?*  

*Correct Answer is  D: Never*  

### AI Response: (may contain errors)  

To understand why the correct answer to the question is "Never," let's break down the reasoning:

1. **Correct Answer: Never**
   - Climbing a tower without a helper or observer is never safe due to the inherent risks involved. If an accident occurs, such as a fall or medical emergency, having someone present is crucial for providing immediate assistance or calling for help. Safety regulations and best practices in tower climbing emphasize the importance of having a buddy system to ensure safety.

2. **Why the Other Choices are Incorrect:**
   - **A: When no electrical work is being performed**
     - This choice suggests that it might be safe to climb if electrical work is not involved. However, climbing a tower poses risks regardless of the type of work being done. Falls can happen at any time, and having a helper is essential for safety.
   
   - **B: When no mechanical work is being performed**
     - Similar to choice A, this implies that the absence of mechanical work makes it safe to climb alone. The risks of climbing, such as falls or equipment failure, are present regardless of the nature of the work being done.
   
   - **C: When the work being done is not more than 20 feet above the ground**
     - This choice suggests that climbing to a height of 20 feet or less is safe without a helper. However, falls from any height can result in serious injury or death. Safety protocols recommend having a helper at all times, regardless of the height.

3. **Useful Rules of Thumb:**
   - Always use a buddy system when climbing towers.
   - Follow OSHA (Occupational Safety and Health Administration) guidelines for tower safety.
   - Ensure that safety equipment, such as harnesses and helmets, is used properly.

In summary, the safest practice is to never climb a tower alone, as the risks involved necessitate having someone present to assist in case of an emergency.