## Core Concept
The question requires understanding the types of epidemiological studies and their applications. **Epidemiological studies** are crucial for understanding the distribution and determinants of health and diseases in populations. The study described involves analyzing the incidence of malaria across various demographic groups (age and sex) within a defined area (a village).

## Why the Correct Answer is Right
The correct answer, **C. Cross-sectional study**, is appropriate for this scenario because cross-sectional studies involve looking at defined populations at a single point in time or over a short period. These studies are useful for **descriptive epidemiology**, allowing researchers to estimate the incidence and prevalence of diseases, as well as identify potential risk factors across different subgroups within the population, such as age and sex.

## Why Each Wrong Option is Incorrect
- **Option A: Case-control study**. This type of study is used to identify factors that may contribute to a medical condition by comparing subjects who have that condition (the "cases") with patients who do not have the condition but are otherwise similar (the "controls"). It's not ideal for directly measuring incidence across various demographic groups.
- **Option B: Cohort study**. This involves following two groups (cohorts) over time: one that has been exposed to a potential risk factor and one that has not. While cohort studies can provide valuable information on incidence and risk factors, they are typically more resource-intensive and not necessary for a straightforward assessment of disease incidence across age and sex groups at a single point.
- **Option D: Experimental study**. This involves interventions (like drug treatments or exposures) being applied to subjects and outcomes measured. It's not suitable for simply observing and describing the incidence of a disease across demographic groups.

## Clinical Pearl / High-Yield Fact
A key point to remember is that **cross-sectional studies** provide a snapshot of a population at a single point in time and are particularly useful for assessing the **prevalence** of a condition. However, they can also give clues about **incidence** when combined with the duration of the disease. This study design is often used in **surveillance** and for generating hypotheses about disease etiology.

## Correct Answer: C. Cross-sectional study.