At what rate does the temperature drop for every 1000 feet gained in elevation?

The correct answer is based on the general principle known as the "lapse rate," which describes how temperature decreases with an increase in altitude in the atmosphere. Specifically, the standard lapse rate is approximately 3.5 degrees Fahrenheit (or about 6.5 degrees Celsius) for every 1000 feet gained in elevation.

If we look closely at the options provided, the rate of 4 degrees, while it might seem reasonable, is below the commonly accepted range. Thus, while none of the options directly reflect the actual standard lapse rate of 6.5 degrees Celsius per 1000 feet, choosing 4 degrees as an answer might lead to underestimating the temperature drop. The correct answer chosen reflects a common approximation used when simplifying discussions about altitude and its effect on temperature. Recognizing the key fact that temperature indeed decreases with altitude is essential for understanding the principles of mountain warfare and environmental conditions encountered by military personnel in mountainous terrains.

So, the answer reflects a reasonable approximation that helps in practical scenarios, but it's important to be aware of the broader context of lapse rates and their variations based on conditions.