Which IV catheter gauge is most commonly used for routine IV therapy in adults?

Rationale: A. 18-20 gauge is correct because these gauges provide a balance between adequate flow rate and patient comfort. They are commonly used for routine IV fluid administration, medication delivery, and blood transfusions in adult patients. B. 14-16 gauge is incorrect because these are large-bore catheters typically used for trauma, surgery, or rapid fluid resuscitation. Using such large catheters for routine therapy can be unnecessary and more painful for the patient. C. 25 gauge is incorrect because this is a very small catheter, usually reserved for pediatric or geriatric patients with fragile veins, or for IV access when minimal flow is required. It is not suitable for routine adult IV therapy due to slow flow rates. D. 22-24 gauge is incorrect because while smaller gauges are sometimes used in adults with difficult veins or for short-term therapy, the 18-20 gauge remains the standard for routine adult IV therapy, balancing flow and patient comfort.