Final answer:
The suspect from the list provided that most closely matches the FBI psychological profile of Jack the Ripper is Sir William Gull, Queen Victoria's physician, due to his medical knowledge and residence in Britain at the time of the crimes.
Step-by-step explanation:
The question concerns the infamous unsolved case of Jack the Ripper, a serial killer active in the Whitechapel district of London in the late 19th century. The FBI's psychological profile of Jack the Ripper suggests that the suspect would likely be a male, suffering from a psychosis, potentially with medical knowledge, and residing in the Whitechapel area during the killings. Of the suspects listed: a) Montague John Druitt, b) Lewis Carroll, c) Sir William Gull, and d) The Marquess of Queensberry, the one that most closely matches the FBI profile, in terms of medical knowledge and being a resident of Britain during the time of the murders, would be Sir William Gull, who was Queen Victoria's physician. It should be noted that the evidentiary support for any Jack the Ripper suspect is largely circumstantial, and Sir William Gull's involvement is one of many theories with no conclusive proof.