Final answer:
The client with numbness and paresthesia in the limb with a cast should be attended to first, as these symptoms could indicate a medical emergency called compartment syndrome, which requires immediate intervention.
Step-by-step explanation:
In prioritizing care for patients, we must assess which condition poses the greatest immediate risk to the patient's health and requires urgent intervention. The client who has a cast on the left leg and reports numbness and paresthesia (B) should be cared for first because these symptoms could indicate compartment syndrome, a condition where pressure within the muscles builds to dangerous levels. This can decrease blood flow, preventing nourishment and oxygen from reaching nerve and muscle cells, and is a medical emergency.
The client with type 1 diabetes mellitus and a slightly elevated fasting blood glucose level (C) should be monitored and managed according to their insulin regimen, but this is not immediately life-threatening. A patient with pneumonia and a fever of 38° C (101° F) (D) is likely already being managed with antibiotics and fever reducers, and although they should be closely monitored, this does not constitute a medical emergency. Lastly, the client who has diarrhea and requests clear liquids for breakfast (A) has the least acute situation and can be managed with dietary adjustments and hydration.