A) multiplying the average times for each stage of mitosis in a particular cell type. B) averaging the percentage of students who are female in many large school populations. C) the number of males divided by the number of females multiplied by 1,000 for people of a particular age. D) 1,000 minus the number of whichever sex is in excess. E) the number of Y chromosomes in a population divided by one-third the number of X chromosomes.