* Blood types are categorized based on the presence or absence of certain antigens on red blood cells. The most common system is the ABO system (A, B, AB, O) and the Rh system (positive or negative).
* OPOS is not a recognized blood type designation. It's possible you're thinking of:
* O-negative: This is a blood type that is considered the universal donor because it lacks both A and B antigens and the Rh factor.
* "O positive" is another common blood type.
If you're trying to determine your blood type, it's important to get tested by a medical professional. Don't rely on online resources or self-diagnosis.