Final answer:
Option B, which phrases the process of assessing vital signs in a friendly and non-threatening way, is the best approach for a nurse to take with a 4-year-old.
Step-by-step explanation:
The best approach for a nurse to assess the vital signs of a 4-year-old would be option B) "I am going to see how warm you are and give your arm a hug." When dealing with children, it's often helpful to use language and descriptions that are friendly and not intimidating. Explaining the process in terms that are familiar and non-threatening to a child can help make the experience less scary and more cooperative. This description of taking temperature and blood pressure is both age-appropriate and non-technical, which is suitable for a 4-year-old's understanding.