Finish the following sentence with the best choice: How to make sure picture frame is level.

Choices:
- Place level on top of picture frame. Make sure bubbles are completely straight across the horizontal line on the level.
- Place ruler on top of picture frame. Make sure bubbles are completely straight across the horizontal line on the ruler.

Answer:
Place level on top of picture frame. Make sure bubbles are completely straight across the horizontal line on the level.