The correct answer is: B. Have been working
The sentence is in the present perfect continuous tense, which is used to talk about an action that started in the past and continues up to the present. The past participle of “work” is “worked,” so the correct form of the verb to use is “have been working.”
The other options are incorrect because they do not use the present perfect continuous tense. Option A, “have been worked,” is in the passive voice, which is not appropriate for this sentence. Option C, “would have working,” is in the conditional perfect, which is used to talk about an action that would have happened if something else had happened. Option D, “had worked,” is in the past perfect, which is used to talk about an action that happened before another action in the past.
Here is a rewritten version of the sentence to make it clearer:
I have been working on this project for months without success.