**Core Concept**
The question is testing the knowledge of the World Health Organization's (WHO) recommended water supply per person per day. This is an essential aspect of public health, particularly in the context of water-borne diseases and sanitation.

**Why the Correct Answer is Right**
The WHO recommends a minimum of 2 liters of water per person per day for drinking, cooking, and personal hygiene. This is based on the assumption that the water will be used for basic needs, such as drinking, food preparation, and personal hygiene, rather than for washing clothes, cleaning, or other non-essential purposes. The recommended water supply is intended to prevent dehydration, diarrhea, and other water-borne diseases.

**Why Each Wrong Option is Incorrect**
**Option A:** 1 liter of water per person per day is considered inadequate, as it may not be sufficient to meet basic needs, particularly in hot and humid climates.
**Option B:** 3 liters of water per person per day is excessive, as it may lead to unnecessary water waste and increased water treatment costs.
**Option C:** 5 liters of water per person per day is also excessive, as it may not be necessary for most individuals, particularly in areas where water is scarce.

**Clinical Pearl / High-Yield Fact**
It's essential to note that the WHO's recommended water supply per person per day may vary depending on factors such as climate, age, sex, and physical activity level. Additionally, the recommended water supply may need to be adjusted for individuals with specific medical conditions, such as diarrhea or vomiting.

**Correct Answer: C. 5 liters of water per person per day is the maximum recommended by the WHO, but 2 liters is the minimum. However, the question is asking for the adequate water supply, which is 2 liters of water per person per day.**