In this investigation, the splash size produced when an object is dropped into water can be influenced by the object's mass and the height from which it is dropped. Since the student dropped several objects from the same height (2 meters), the key factor affecting the splash size is likely the mass of the objects.
Given the rankings for splash size, object W has a ranking of 2, which indicates that it produces a relatively larger splash than object Y (ranking 1) but a smaller splash than object Z (ranking 3) and object X (ranking 4).
Since the object that produced the largest splash (ranking 4) is object X, it is likely that object X has the greatest mass compared to the other objects. Therefore, the answer to which object most likely has the greatest mass is:
object X.