What Makes Market Segmentation an Important Variable in Strategy Implementation

What makes market segmentation an important variable in strategy implementation?

A) It allows a small firm to compete successfully with a large firm.
B) It allows a firm to operate with limited resources.
C) New or improved market-segmentation approaches are required for the successful execution of market development & market penetration.
D) Market segmentation decisions directly affect marketing mix variables.
E) All of the above