Final answer:
Option D, the history of school systems in many of the states in the United States, is excessively broad for research due to the extensive time and numerous different education systems involved.
Step-by-step explanation:
The best example of a topic that is too broad would be D. the history of school systems in many of the states in the United States. This subject is vast as it encompasses a substantial historical period and a large geographical area with numerous individual education systems. Narrowing it down to specific states, time periods, or aspects of the school systems would make it more manageable and focused for a research project or a detailed study.