Final answer:
The nurse cannot accurately determine the age of a bruise based solely on its appearance.
Step-by-step explanation:
The nurse cannot determine the exact number of days the bruise is old based solely on its appearance. The color of a bruise changes as it heals, starting with a red or purple color and then transitioning to green or yellow before fading away. The nurse can estimate the age of a bruise based on its appearance, but it is not an exact science. It is important to note that the appearance of a bruise can vary depending on the individual and other factors, such as skin tone.
In the clinical scenarios provided, there is no specific mention of a 4-year-old with a large green bruise on the thigh. Therefore, without additional information, it is not possible to accurately estimate the age of the bruise.