**Core Concept:**
The question is asking about a non-deliberate cultural practice that has an anti-mosquito effect. Mosquitoes are known to transmit various diseases such as malaria, dengue, Zika, and chikungunya. Understanding these practices can help prevent mosquito-borne illnesses.

**Why the Correct Answer is Right:**
The correct answer, **C. Mosquito repellents**, refers to substances used to deter mosquitoes from landing or biting humans. These can be chemical compounds or natural substances. The use of mosquito repellents is a deliberate method to prevent mosquito bites, which indirectly reduces the risk of mosquito-borne diseases.

**Why Each Wrong Option is Incorrect:**

A. **Natural repellents (Option A)**: While certain plants and essential oils do have mosquito-repelling properties, they are not considered a deliberate cultural practice and are often less effective than commercial repellents.

B. **Wearing light-colored clothing (Option B)**: Although mosquitoes are more attracted to darker colors, this practice is not a specific method for preventing mosquito bites and does not guarantee protection.

D. **Using bed nets (Option D)**: Although bed nets can protect against mosquito bites while sleeping, they are not considered a general non-deliberate cultural practice in various societies.

**Clinical Pearl (High-Yield Fact):**
The **use of mosquito coils** (Option C) is a common cultural practice in some regions to deter mosquitoes. Mosquito coils release pyrethrum smoke that has insecticidal properties, effectively preventing mosquito bites and reducing the risk of mosquito-borne disease transmission.

**Correct Answer:** C. Mosquito repellents

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In conclusion, mosquito repellents are considered a deliberate method to prevent mosquito bites and, subsequently, reduce mosquito-borne disease risk. Mosquito coils, however, are a common cultural practice but are not specifically focused on preventing mosquito bites and are not as universally applicable as repellents. For a global perspective, mosquito coils are more prevalent in certain regions, while mosquito repellents are used in various regions worldwide as a deliberate preventive measure against mosquito bites.