In which of the following conditions pseudopolyps are seen?

Islands of regenerating mucosa called pseudopolyps can be seen in ulcerative colitis. These are seen during a quiescent phase of ulcerative colitis and are a later manifestation of this condition. Ref: Robbin's 7th edition page 851, Harrison's Internal Medicine 17th edition chapter 26 ; Colon and Rectal Surgery, 5e By Marvin L. Corman, 2005, Page 1330.