Final answer:
A stuffed animal is the most appropriate toy for 5-year-old Eva during her unsupervised time in the hospital. It offers comfort without the risks associated with other toys. For dehydration, isotonic saline is typically administered intravenously.
Step-by-step explanation:
For 5-year-old Eva, who has been admitted with dehydration and requires intravenous rehydration, the most suitable toy to play with while unsupervised would be a stuffed animal. Unlike puzzles and coloring books which involve multiple parts and could pose a choking risk or require supervision to prevent mess, a stuffed animal is safe, comfortable, and familiar, providing comfort without the need for constant supervision.
When a human patient is dehydrated and needs to be given fluids intravenously, they are often given a solution such as saline at a concentration that is isotonic with respect to body fluids. This helps to ensure that the electrolyte balance is maintained and that the patient is rehydrated effectively without causing harm or further imbalance.