Final answer:
The most measurable client anxiety goal is for the client to report anxiety at less than 3 out of 5 by discharge, due to its specificity and quantifiability.
Step-by-step explanation:
The goal that best exemplifies measurability in terms of client anxiety is: Client will report anxiety at less than 3 out of 5 by discharge. This goal is specific and quantifiable, as it involves a numerical value on a set scale that reflects the client's self-reported level of anxiety and can be directly measured. Compared to the other options, it provides a clear, objective, and measurable outcome.