Which of the following statements regarding sector indexes is most accurate?
A. track different economic sectors and cannot be aggregated to represent the equivalent of a broad market index.
B. provide a means to determine whether an active investment manager is more successful at stock selection or sector allocation.
C. apply a universally agreed upon sector classification system to identify the constituent securities of specific economic sectors, such as consumer goods, energy, finance, health care.
The correct answer is B.
However, the book did not explain why C is incorrect. I understand why A is wrong (should be "can be aggregated to represent…), and B is obviously right. Can someone explain why C is incorrect?