The correct answer is (c) 1.5
The best I can explain: The X/A ratio is the ratio of the number of X-chromosomes and the set of autosomes. The X/A ratio of super females of Drosophila is 1.5. The X/A ratio of normal females, intersex, and super males of Drosophila is 1, 0.67, and 0.33 respectively.