Final answer:
The water cycle is ultimately fueled by solar energy from the Sun's warmth, causing evaporation and condensation of water in the atmosphere.
Step-by-step explanation:
The water cycle is ultimately fueled by solar energy. The energy from the Sun warms the oceans and other surface waters, causing evaporation and sublimation of water. This leads to the formation of water vapor in the atmosphere, which eventually condenses into clouds and precipitates back to Earth as rain or snow. Solar energy is the primary driver of the water cycle.