Final answer:
The correct CPR compression to ventilation ratio for a single rescuer of a 3-year-old child is 30 compressions to 2 ventilations.
Step-by-step explanation:
The correct compression to ventilation ratio for a single rescuer performing CPR on a 3-year-old child is 30 compressions to 2 ventilations. This ratio is recommended to ensure that the child receives both adequate circulation and oxygenation. It is important for rescuers to also give breaths gently and to avoid providing too much volume, which can cause air to enter the stomach and potentially lead to complications.