Answer: D. 60
Important Concept: Fractions, Percentage
Key Concept: This question does not directly relate to a specific AP US History key concept as it is a mathematical question.
Explanation: The question is asking for three-fifths (or 60%) of 100. To find this, you multiply 100 by 0.60 (which is the decimal equivalent of three-fifths or 60%). The result is 60. Therefore, three-fifths of 100 is 60.