A subscription business wants to understand whether its customers fall into natural groups it has not thought of, so that marketing can be tailored. It has three years of behavioural data and no existing segment labels. Which learning approach fits?

• ASupervised learning, specifically classification.
• BUnsupervised learning, specifically clustering.
• CSupervised learning, specifically regression.
• DReinforcement learning, because the marketing team will act on the result.