Final answer:
The minimum acceptable IOA in ABA is often considered to be 80%, but 90% is preferred for reliability, so the answer is C. 90%.
Step-by-step explanation:
The minimum acceptable Interobserver Agreement (IOA) in Applied Behavior Analysis (ABA) is generally considered to be 80%. However, a higher IOA of 90% is often preferred as it suggests a more reliable measurement of behaviors being studied. Therefore, the correct answer is C. 90%. IOA is a significant measure in ABA as it reflects the degree to which different observers report the same observed values after measuring the same events.