*Question E4A10:
Which trigger mode is most effective when using an oscilloscope to measure a linear power supply’s output ripple?*  

*Correct Answer is  D: Line*  

### AI Response: (may contain errors)  

To measure a linear power supply's output ripple using an oscilloscope, the most effective trigger mode is **Line**.

### Explanation:

1. **Why the correct answer is correct (Line):**
   - The **Line** trigger mode synchronizes the oscilloscope's trigger with the AC line frequency (usually 50 or 60 Hz). This is effective for measuring power supply ripple because the ripple is typically related to the AC line frequency. By using the Line trigger, the oscilloscope can stabilize the display of the ripple waveform, making it easier to analyze.

2. **Why the other choices are incorrect:**
   - **Single-shot (A):** This mode captures a single event and is not suitable for continuous signals like power supply ripple, which needs ongoing monitoring.
   - **Edge (B):** While Edge triggering is useful for capturing transient events, it is not ideal for continuous periodic signals like ripple, as it may not synchronize well with the AC line frequency.
   - **Level (C):** Level triggering is used to trigger the oscilloscope when the signal reaches a specific voltage level. This is not effective for periodic signals like ripple, which are better synchronized with the AC line frequency.

### Useful Rule of Thumb:
- For periodic signals related to the AC line frequency, such as power supply ripple, use the **Line** trigger mode to achieve a stable and clear waveform display.