Explanation

$X$ = 1, 3 $Y$ = 4. Drosophila have 3 pairs of autosome and one pair sex chromosome. Sex determination in Drosophila is exactly similar to the human beings, i.e., female is homogenetic and male is heterogametic. In the given diagrams, ‘A’ belongs to the female Drosophila and ‘B’ belongs to the male Drosophila 1 indicates = X-chromosomes in female Drosophila 2 indicates = Autosome 3 indicates = X-chromosomes in male Drosophila 4 indicates = Y-chromosome in male Drosophila