Final answer:
During single rescuer CPR, the compression-to-ventilation ratio is 15 compressions to 1 breath, as it ensures adequate blood flow while providing necessary oxygenation.
Step-by-step explanation:
The correct answer is C. 15 compressions to 1 breath. During single rescuer CPR, it is recommended to use a compression-to-ventilation ratio of 15:2 for both adults and children, with one exception for infants, where the ratio is 30:2. This means that for every 15 compressions performed, one breath should be given. This ratio ensures adequate blood flow while providing necessary oxygenation.