A graduated cylinder would be the most appropriate tool to measure out 50 mL of water. Graduated cylinders are designed specifically for measuring volumes of liquids and they are typically accurate to within 1 mL or less. To measure 50 mL of water with a graduated cylinder, you would pour the water slowly into the cylinder while keeping it level with your eyes at the level of the meniscus (the curved surface of the water in the cylinder) and stop pouring once the bottom of the meniscus reaches the 50 mL mark on the cylinder. It's important to note that the accuracy of the measurement depends on the precision of the graduated cylinder being used, as well as the skill of the person making the measurement.