To determine which object most likely has the greatest mass based on the splash size rankings, we can analyze the information provided. The splash size indicates the impact of the object when it hits the water, which can be influenced by the mass of the object.
The rankings provided are:
- Object W: 2 (medium splash)
- Object X: 4 (largest splash)
- Object Y: 1 (smallest splash)
- Object Z: 3 (large splash)
Since object X has the highest splash size ranking (4), it suggests that object X most likely has the greatest mass. The larger the mass of an object, the greater the force it exerts upon hitting the water, leading to a larger splash.
Thus, the answer is: object X