The best option for this example is to use the function average because we can to know the average of people in those five years, this function will sum all the people and then will divide by the years, in this case 5 years, for example =average(23+12+33+26+19)/5 this is equal to 23, median and mode only return the number most repeated in a range, and min return the less value in a range.
Pipeline hazard prevents other instruction from execution while one instruction is already in process. There is pipeline bubbles through which there is break in the structural hazard which preclude data. It helps to stop fetching any new instruction during clock cycle.