People with type o-negative blood are universal donors. that is, any patient can receive a transfusion of o-negative blood. only 12.4% of the american population have o-negative blood. if 8 people appear at random to give blood, what is the probability that at least one of them is a universal donor?

There is a 0.992:8 or 1:8 ratio/probability that at least one of the donors is a type O blood type or a universal donor. 12.4% was multiplied with the current number of population which is 8, and the result is 0.992 or 1% chance. This means that 1 out of 8 of the donors are O type and can become a universal donor; the rest of the population are a mixture of the other blood types.  

The answer is b) gene