Final answer:
Geothermal power (option C) is the least weather-dependent alternative energy source among the options given, as it utilizes the Earth's consistent internal heat, unlike wind or solar energy, which rely on variable weather patterns.
Step-by-step explanation:
Out of the alternative energy sources listed, geothermal power would be expected to be the least dependent upon the weather. Wind power is directly affected by wind patterns, while solar power relies on sunlight which can be intermittent due to changes in weather.
Geothermal energy, on the other hand, harnesses heat from the Earth's interior which is not influenced by weather conditions, making it a more reliable and constant source of energy. It is relatively easy, steady, and well demonstrated in various locations providing electricity and direct heat, despite it not scaling to be a significant part of our entire energy mix due to its dependence on specific geological conditions.
Hence, the correct answer is Option C.