**Core Concept**
A sanitary well should be located to minimize the distance users need to travel to access it, reducing the risk of contamination and promoting safe water use. This principle is based on the concept of accessibility and the importance of reducing the contact between the water and the environment to prevent contamination.

**Why the Correct Answer is Right**
The correct answer is based on the idea that users should not have to travel more than 1/4 mile (400 meters) to access the well. This distance is considered optimal as it minimizes the risk of contamination and promotes safe water use. The farther away the well is located, the greater the risk of contamination from surface water, animal waste, or other environmental sources. This is particularly important in areas with poor sanitation and limited resources.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not specified, so it cannot be evaluated.
* **Option B:** This option is also not specified, so it cannot be evaluated.
* **Option C:** This option is not the correct answer, as it does not align with the principle of minimizing the distance users need to travel to access the well.

**Clinical Pearl / High-Yield Fact**
A key consideration in well location is the slope of the surrounding terrain. A well should not be located in a low-lying area where water may collect and increase the risk of contamination.

**Correct Answer: C. 400 meters**