[Poll] Which among the following is an Unsupervised Machine Learning Algorithm?

24 hour poll on Twitter and LinkedIn, started at 9:57 PM on 13/4/21

Twitter: https://twitter.com/JovianML/status/1382007654717943810?s=20
LinkedIn: https://www.linkedin.com/posts/jovianai_machinelearning-artificialintelligence-activity-6787773277344550912-krF6