All else being equal, which of the following locations is likely to have the coolest climate?

The option indicating a city located at 6,000 feet above sea level is likely to have the coolest climate due to the principle of altitude. As elevation increases, the temperature generally decreases. This is attributed to the thinning of the atmosphere at higher altitudes, which leads to lower air pressure and cooler temperatures.

In comparison, a city located at sea level near the Equator would typically experience a warm climate year-round due to its proximity to direct sunlight, which is more intense at the equator. A city near the poles would experience extreme cold but could still have seasonal variations, potentially making its summers relatively mild. Lastly, a city in a desert region often receives plenty of sunlight, leading to high temperatures, especially during the day. Thus, while all options present different climatic conditions, the elevation of 6,000 feet most consistently contributes to cooler temperatures, making this choice the best answer.