Which of the following tasks requires unsupervised learning?

Group of answer choices

Netflix predicting what movie a user might want to watch based on other users with similar tastes of movie

Facebook identifying the face of a user from a photo based on other photos where the same user's face has been tagged

Email server labeling an email as "spam" or "not spam" based on its similarity with other emails reported as "spam"

A doctor diagnosing whether a patient has cancer or not by comparing his$/$her medical records and test results to patients diagnosed with cancer