Which of the following is an example of discontinuous variation observed in man?

Tongue rolling is an example of discontinuous variation observed in man. Discontinuous variation refers to distinct categories or traits that are either present or absent in a population. In the case of tongue rolling, some individuals can roll their tongues while others cannot, making it a clear example of a trait that is either present or absent without any intermediate variations. This is different from continuous variation, which refers to traits that vary along a continuum, such as height or body weight.