Today in The Post, I review the gargantuan 110-disc collector’s set that MGM has issued to celebrate the 90th anniversary of United Artists, which MGM is re-launching as a specialty label. There are an awful lot of great movies here, but MGM declined to make anyone available to answer my questions, of which there were many. Why was there no documentary or book delving into the studio’s history and acknowledging Arthur Krim and Robert Benjamin, who rescued UA from near-demise under Mary Pickford and Charlie Chaplin and turned it into Hollywood’s predominant studio of the ’50s, ’60s and ’70s? Why doesn’t the box include any of the great UA titles produced by Samuel Goldwyn (“The Hurricane,” “The Westerner,” “Dodsworth”), Alexander Korda (“The Four Feathers”) and David O. Selznick (the Oscar-winning “Rebecca” for starters) that MGM has already issued on DVD? For that matter, where’s “Exodus” (or any of Otto Preminger’s other UA titles)? “Sweet Smell of Success?” “The Vikings”? Or for that matter, the Oscar-winner “Tom Jones,” which is currently part of the MGM-leased Goldwyn library? Among more recent UA titles, why didn’t they include “Ghost World,” a better indie than than “Pieces of April”? And MGM’s part owner, Sony, would probably have been glad to share its rights to “Capote,” the most recent UA title to be nominated for Best Picture. As I note in the piece, many key UA titles long ago passed into other hands — Warners has most of Charlie Chaplin’s titles, “Stagecoach,” “Foreign Corrrespondent” and “One Flew Over the Cuckoo’s Next” on DVD, while Paramount controls rights to “The African Queen,” “High Noon” and the original “The Invasion of the Body Snatchers.” But why did MGM mystifyingly choose to open the set with “The Woman in the Window,” an International Pictures production originally released by RKO (as clearly specified in the poster included in the album containing the discs) rather than the two early UA titles it actually does still control? “Coquette” (1929) features an Oscar winning performance by UA co-founder Mary Pickford, no less, and “Hallelujah, I’m a Bum” (1933) is an endearingly oddball musical starring Al Jolson. If you’re asking collectors to fork over $670 for a DVD box, you really have to go the extra mile, guys, and not give them Sidney Poitier in “The Wilby Conspiracy” when they’d rather have his Oscar winner, “Lillies of the Field.”