The correct option is C They are poor models for New Towns.
Option (a) can be struck off as author does not believe in the efficiency of New Towns/Suburbs at all. Option (b) can be struck of as author believes new problems rather than the ones that are affecting existing cities will affect suburbs. Option (d) is wrong as the author believes that prices at suburbs will increase as wealthier people will tend to move first. Option (e) is wrong as the author believes that it will solve none of the problems if adapted in existing fashion. Hence option(C) is the answer.