The phrase describes a misuse of Public Interest Litigation (PIL). 'Ostensibly' means 'apparently' or 'on the surface'. So, the phrase means that on the surface, the PIL appears to be for a public cause, but its real, hidden motive ('in fact') is to advance a personal or private agenda. This could be a business rivalry, a personal grudge, or for publicity. Such PILs are considered an abuse of the process of the court. Option (d) perfectly captures this meaning of a hidden private motive behind the facade of public interest.