Final answer:
Australopithecine skeletons are most likely skeletons of humans, as they exhibit characteristics of both apes and modern humans, with evidence of bipedalism.
Step-by-step explanation:
Australopithecine skeletons, particularly the pelvis and legs, are most likely skeletons of humans (b). The Australopithecus species, such as Australopithecus afarensis, exhibited characteristics of both apes and modern humans. While their long arms and curved finger and toe bones suggest a tree-dwelling behavior similar to apes, the shape of their pelvis indicates bipedalism, a characteristic shared with modern humans. This evidence suggests that Australopithecus species were intermediate between apes and humans in terms of locomotion.