What is water displacement?

Which principle is used to determine the volume of an object using water displacement?

Which of the following steps correctly describes the process of measuring water displacement to find the volume of an irregularly shaped object?

If the initial water level in a graduated cylinder is 10.0 mL and the final water level after submerging an object is 13.5 mL, what is the volume of the object?

A rock is placed in a graduated cylinder, causing the water level to rise from 20.0 mL to 25.5 mL. If another rock is added, and the water level rises to 30.0 mL, what is the combined volume of the two rocks?