Explanation:

- Option 1: Ice caps

- Ice caps and glaciers hold the majority of Earth's fresh water.

- They are primarily found in polar regions like Antarctica and Greenland.

- Option 2: Inland seas

- Inland seas contain some fresh water but not nearly as much as ice caps or glaciers.

- They are relatively small in volume compared to other sources.

- Option 3: Atmosphere

- The atmosphere does contain water vapor.

- However, this amount is minimal compared to other water sources.

- Option 4: Groundwater

- Groundwater is a large reservoir of fresh water on Earth.

- It is the largest source of liquid fresh water.

- Correct Answer: Option 1: Ice caps

- Ice caps contain the most fresh water on Earth.