Final answer:
The correct code for a returning patient receiving a thoracic spine x-ray and a shot of Morphine is 99214. This code describes an established outpatient visit with detailed examination and moderate decision-making complexity.
Step-by-step explanation:
The appropriate code for a returning patient who receives a thoracic spine x-ray and shot of Morphine would be E. 99214. This code is for an established office or other outpatient visit, typically 25 minutes, involving a detailed examination and low to moderate complexity decision-making.
Codes 99203 and 99204 are for new patients, which does not apply to the scenario. Code 99205 is also for a new patient but denotes a higher complexity and time. The 99215 code reflects a high complexity visit for established patients, which may not match the described services unless more complex decision-making beyond the shot and x-ray was required.