Which of the following is an example of unsupervised learning?

Unsupervised learning refers to a type of machine learning where the model is trained on data without labeled responses. The goal is to identify patterns or groupings within the data itself. Market segmentation is a prime example of unsupervised learning because it involves grouping a set of customers based on their behaviors or characteristics without prior knowledge of the segments. This process allows businesses to identify distinct groups within their customer base, which can inform marketing strategies and tailored offerings.

In contrast, spam detection and email classification are forms of supervised learning, where the model is trained on labeled data (i.e., emails marked as "spam" or "not spam"). Image recognition typically also falls under supervised learning, as it usually involves training on labeled images to recognize specific objects or features within those images. In summary, market segmentation exemplifies unsupervised learning by utilizing data patterns to form clusters without explicit guidance or labels.