To determine which object most likely has the greatest mass based on the provided splash size rankings, we can analyze the information given:
- Object W has a splash size ranking of 2.
- Object X has a splash size ranking of 4.
- Object Y has a splash size ranking of 1.
- Object Z has a splash size ranking of 3.
Since the splash size ranking indicates that object X (ranking 4) creates the largest splash, it is reasonable to infer that it likely has the greatest mass, as larger mass typically results in a larger splash when dropped into water.
Therefore, the object most likely to have the greatest mass is:
object X