Final answer:
The Numeric Pain Intensity Scale is the least appropriate tool for assessing pain in a 4-year-old due to their limited understanding of numerical quantification of pain.
Step-by-step explanation:
The tool that would be least appropriate to use when assessing a 4-year-old child's pain is D) Numeric Pain Intensity Scale. This scale, which usually requires patients to rate their pain on a scale from 0 to 10, is not well-suited for young children who may not have a full understanding of numbers or how to quantify their pain in such a manner.
More age-appropriate tools that rely on visual representations of pain, such as the FACES Pain Rating Scale or the Oucher Pain Rating Scale, are typically used for young children. The Poker Chip Tool, another visual analog scale where children can use pieces to represent their pain, is also more suitable for young children than the numeric scale.