**Core Concept**
Anti-larval measures are public health strategies aimed at preventing the breeding and growth of larvae, particularly those of disease-causing insects like mosquitoes. These methods are essential in controlling the spread of vector-borne diseases such as malaria, dengue, and filariasis.

**Why the Correct Answer is Right**
Malathion is an organophosphate insecticide primarily used as an adulticide to kill adult mosquitoes and other flying insects. While it can provide temporary relief by reducing the adult mosquito population, it does not target larvae directly and is not considered an anti-larval measure. In contrast, the other options directly target the larval stage of mosquitoes.

**Why Each Wrong Option is Incorrect**
**Option A:** Intermittent irrigation is a method used to prevent the breeding of larvae by disrupting the larval habitat. It involves periodically draining water from areas where mosquitoes breed, making it an effective anti-larval measure.
**Option B:** Paris green is a toxic substance used to kill mosquito larvae in standing water. It is an effective anti-larval agent, particularly useful in controlling the spread of malaria.
**Option C:** Gambusia affinis, also known as the mosquito fish, is a species of fish that feeds on mosquito larvae. It is a biological control method used to prevent the breeding of mosquitoes and is an anti-larval measure.

**Clinical Pearl / High-Yield Fact**
When implementing anti-larval measures, it is essential to identify and eliminate potential breeding sites, such as standing water, stagnant pools, and areas with poor drainage. This can be achieved through a combination of physical, chemical, and biological methods.

**Correct Answer:**
✓ Correct Answer: D. Malathion