Which of these people could be practicing anabaptism
a. a man who refuses to be baptized at all
b. a man who baptizes his infant son at birth
c. a man who argues that no one should be baptized
d. a man who chooses to be baptized as an adult

A man who chooses to be baptized as an adult is practicing Anabaptism.

To add, Anabaptists are Christians who believe that baptism is only valid when the candidate confesses his or her faith in Christ and wants to be baptized. This believer's baptism is opposed to baptism of infants, who are not able to make a conscious decision to be baptized.

d. a man who chooses to be baptized as an adult