Concept:
Market segmentation is the process of dividing a broad market into smaller groups based on characteristics like age, income, or preferences.
Step 1: Understand the definition.
\[
{Dividing market into groups} \Rightarrow {segmentation}
\]
Step 2: Evaluate options.
- (A) Market expansion $\times$ increasing market size
- (B) Market segmentation \checkmark correct
- (C) Product development $\times$ creating new products
- (D) Brand positioning $\times$ creating brand image
Hence, the correct answer is Market segmentation.