The correct answer is (C) Intruder; meddler; one who intrudes on the property of another; someone who meddles in the affairs of another; to intrude into a field of endeavor or region without proper authorization.

Interloper comes from Inter + loper (leap).

Examples of use:

• We were prepared to use force to expel any interlopers from our property.
• To his chagrin, interlopers effectively destroyed the meeting's utility.