The correct Active/Passive form of the given sentence is:

☀ The wife of a police Inspector of Rajnagar Chowky had been killed by him in this room before the sunrise.

Explanation for other options:

☀ The wife of a police Inspector of Rajnagar Chowky were killed by him in this room before the sunrise. This option uses "were killed," which is not the correct verb form for the passive construction. The correct form should be "had been killed" to match the past perfect tense used in the original sentence.

☀ The wife of a police Inspector of Rajnagar Chowky had been killing by him in that room. This option changes the meaning of the sentence by using "had been killing" instead of "had been killed." The original sentence states that the wife was killed, not that she was doing the killing.

☀ The wife of a police Inspector of Rajnagar Chowky has been killing by him in that room before the sunrise. This option uses "has been killing," which is in the present perfect tense and does not match the past tense used in the original sentence. The correct form should use "had been killed" to match the past perfect tense used in the original sentence.