Final answer:
A graduated cylinder is the most appropriate device to measure 9 mL of an oral medication due to its ability to provide accurate and precise measurements in milliliters.
Step-by-step explanation:
When measuring a volume of 9 mL of an oral medication, the most appropriate measuring device would be a graduated cylinder, which gives precise measurements and is typically used in healthcare and laboratory settings. Graduated cylinders have volume markings for milliliters and allow users to accurately measure liquids. The cylinder can be read by aligning the bottom of the meniscus with the volume marking, ensuring that the measurement accounts for the curve of the liquid surface. Alternately, a burette can offer even more precise measurements, often to the nearest 0.01 mL, but for a simple oral medication dose, a graduated cylinder would suffice.