Final answer:
The 'six degrees of separation' concept tested by Stanley Milgram aimed to explore the interconnectedness of human social networks, demonstrating that people are closer connected than they may think.
Step-by-step explanation:
In the term 'six degrees of separation,' the research undertaken by Stanley Milgram aimed to test the interconnectedness of human social networks. Specifically, this refers to the small-world problem, which is the idea that all people are six, or fewer, social connections away from each other. As such, the answer to the student's question is (c) The interconnectedness of human social networks.
It's important to note that Milgram's other research also delved into obedience to authority. His most famous experiment involved participants administering what they believed were electric shocks to others, demonstrating a high level of obedience to authority figures.