There are two kinds of water, fresh and salt water. Salt water is found in the ocean, which means that any answer with salt water, or the ocean, in it is not a correct source of freshwater. A, B, and D, all include the ocean as their answer, which means that they all include salt water, so C is the only option left. Lakes, rivers, water vapor, and ice sheets are all examples of sources of freshwater. I hope your sister gets a good grade!
