Which is an example of a binary classification task?

• A. Email spam detection (spam or not spam)
• B. Forecasting quarterly revenue
• C. Recommending products
• D. Clustering customers into segments

Answer: (A)

Binary classification involves predicting one of two possible labels for each input. In email spam detection, every email is labeled as either spam or not spam, so there are exactly two classes and the task is to assign one of them to each message. This contrasts with forecasting quarterly revenue, which predicts a numeric value (a regression task). Recommending products is about selecting items to suggest and often involves ranking or multi-label decisions rather than a single binary label. Clustering customers into segments is an unsupervised approach that groups data without predefined labels.