Fill in the blank with the correct option.

One evening of each week was set apart by him for the reception of ____ chose to visit him.

Option 1 -> "Whosoever" means "anyone who" and functions as both the object of "of" and the subject of "chose to visit."

Option 2 -> "Whichever" is used for selecting from a set of options, not for referring to people in this context.

Option 3 -> "Whom" is an object form and cannot be the subject of "chose" - we'd need "whom he chose," not "whom chose."

Option 4 -> "Who" alone doesn't convey the meaning of "anyone who" and creates an incomplete relative clause.

Hence, whosoever -> This archaic/formal term meaning "anyone who" or "whoever" fits perfectly in this formal sentence structure, serving as both the object of the preposition "of" and the subject of "chose to visit him" -> correct