Well, it's important to know the context! All of these phrases can be correct, if used in the right context. "had learned" = past perfect tense -> Example: "The students had learned the material, but forgot most of it when they took the exam!" "have learned" = present perfect tense (I / you / they / we) -> Example: "The students have finally learned the material." "has learned" = present perfect tense (he / she / it) -> Example: "The student has finally learned the material." "had been learned" = past perfect tense, passive voice -> "The material had been learned by the students, but it was all forgotten when they took the exam!" "has been learned" = present perfect tense, passive voice -> "The material has been learned by the students, but they still need to revise it." "have been learned" = present perfect tense, passive voice -> "The exam topics have been learned by the students, but they still need to revise it."

At first I am not a native speaker . But I just follow the rules, may be I have mistake. Have been_" present perfect continuous Tense rules : subject+ has been/ have been+ ( verb+ ing) I have been learning English language since last Sunday. He has been reading in this school for three years. Had been ( past perfect continuous Tense) subject+ had been+ ( verb+ ing) we had been learning... I had been playing.... Your mother had been waiting for you. Thanks