Agile software development and extreme programming are examples of what approach to software development UCD development

iterative and incremental development

the simple model of development

the water fall model of development

Agile Software development and the extreme programming are examples of the iterative and incremental development approach

Explanation:

Agile is probably the most popular of all software development model. In this we design, test, deploy and deliver. And we deliver this everyday and in iterative manner. The client test it and deliver back to team with list amendment required, and team again test deploy and deliver, and process continues till software reaches its final shape.