Why is o the most common blood type

There are 4 main blood groups: A, B, AB and O, of which group O is the most common. In the United States, the average distribution of blood types is as follows: O-positive: 38 percent. O-negative: 7 percent.

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The rate that would change would be the  searching efficiency/attack rate. there are only two other rates in this model: the  growth rate of prey, and the  predator or consumer mortality rate.the  searching efficiency/attack rate is what indicates how effectively can a predator capture its prey whether in the searching process or actual capturing/attacking process.