Answer
The pi bond moved to the oxygen, forming a lone pair.
The oxygen will get a negative charge, and the carbon that was connected to the pi bond will get a positive charge.
Work Step by Step
1. The electronegative atom is the oxygen.
2. Draw the arrows:
Follow the same pattern we have learned in the chapter.
(The pi bond electrons will move to the electronegative atom.)
3. Do the changes based on the arrows.
* Don't forget the formal charges!