Which of the following is NOT a subsystem of Earth's hydrologic system? groundwater glaciers mountains atmosphere

The Earth's system is complex and comprised of four subsystems (hydrologic, biosphere, atmosphere, geosphere) that interact with each other and together form natural processes. The hydrologic system are all waters on Earth. The atmosphere is mixture of gasses that surround the Earth is a subsystem for itself. So, the atmosphere is NOT a subsystem of Earth's hydrologic system.