Which condition is Ringer's Lactate commonly used to treat due to significant fluid loss?

C) Diarrhea

Ringer's Lactate is an intravenous fluid used for fluid and electrolyte replacement. It is commonly administered to patients experiencing significant fluid loss, such as that caused by severe diarrhea, to prevent or treat dehydration and electrolyte imbalances.

The final answer is $\text{C}$.