Which one of the following statements best describes the major difference between sex determination in drosophila and in humans? a. in drosophila, the ratio of x chromosomes to the number of haploid sets of autosomes determines the sex while in humans the presence of the y chromosome determines maleness. b. in drosophila, the absence of a y chromosome determines femaleness while in humans the presence of the y chromosome determines maleness. c. in drosophila, the ratio of x chromosomes to the number of haploid sets of autosomes determines the sex while in humans the presence of at least two x-chromosomes determines femaleness.