Step 1: Understanding the context of the quote.
The phrase "Sociology and Anthropology are twin sisters" was coined by A. L. Kroeber, a prominent anthropologist, to highlight the close relationship between sociology and anthropology. Both fields study human behavior, society, and cultures, but they approach them from different perspectives. Sociology tends to focus on social structures and institutions, while anthropology often studies cultures and human evolution.
Step 2: Conclusion.
A. L. Kroeber is credited with saying that sociology and anthropology are "twin sisters" due to their interconnectedness in studying human societies and cultures.
Final Answer: \[ \boxed{\text{The correct answer is (A) A. L. Kroeber.}} \]