The effect of sex on mathematics achievements is a research?

The effect of sex on mathematics achievements is a research?
(a) Descriptive
(b) Historical
(c) Action
(d) Causal comparative
✅ Correct option: (d) Causal comparative
Explanation: Causal-comparative research studies the effect of one variable (e.g., sex) on another variable (e.g., achievement in mathematics) without manipulation, by comparing groups.