A(n) __ is a well-developed set of ideas that proposes an explanation for observed phenomena. A operational definition B theory C conclusion D hypothesis

## Step 1<br />The problem is asking us to identify the term that best fits the description "a well-developed set of ideas that proposes an explanation for observed phenomena". Let's analyze each option:<br /><br />## Step 2<br />### **Operational Definition**<br />An operational definition is a clear, concise detailed definition of a measure. It is not a set of ideas or explanation for observed phenomena.<br /><br />## Step 3<br />### **Theory**<br />A theory is a well-developed set of ideas that proposes an explanation for observed phenomena. It is a comprehensive explanation of an aspect of nature that is supported by a vast body of evidence.<br /><br />## Step 4<br />### **Conclusion**<br />A conclusion is a final decision or judgment based on reasoning or data. It is not a set of ideas or explanation for observed phenomena.<br /><br />## Step 5<br />### **Hypothesis**<br />A hypothesis is a proposed explanation for a phenomenon that is made as a starting point for further investigation. It is not a well-developed set of ideas.<br /><br />## Step 6<br />Based on the above analysis, the term that best fits the description is "theory".