An action in a sentence can be represented in two ways, namely active and passive voice.
The passive voice always uses the past participle form of the main verb irrespective of any tense. Only the auxiliary verbs depend upon the sentence given in active voice.
The correct answer is C)The man next door has not been seen by anybody since last week.
Option C is correct as to use the words given in the parentheses the subject should remain at its place and been should be added after has not and before seen (using not because of disappeared).
The other options are wrong as is, was , and had cannot be used in the passive form of the given sentence.