Final answer:
The correct function of the geosphere among the provided options is D) Serving as the interface between all spheres. The geosphere interacts with the hydrosphere, atmosphere, and biosphere, contributing to the Earth's system as a whole.
Step-by-step explanation:
The geosphere primarily refers to the solid parts of the Earth, such as its rocks and minerals. Of the options provided for its functions, the most accurate is D) Serving as the interface between all spheres. The geosphere interacts with the hydrosphere, atmosphere, and biosphere in intricate ways. For example, the geosphere and biosphere interact in the cycling of nutrients, the geosphere provides the landscapes that hold bodies of water in the hydrosphere, and mountain ranges within the geosphere affect weather patterns in the atmosphere.
While the geosphere does contribute to a livable climate by, for instance, providing minerals that buffer pH levels in the ocean, this is a result of its interactions with other Earth systems rather than a function in isolation. Additionally, the geosphere itself does not facilitate the movement of water through transpiration nor the process of photosynthesis; these are functions of the biosphere and the hydrosphere, respectively. It is not the sole source of all energy for life either; the primary source is the sun.