A、Their frightening and sorrowful howls. B、Their capability of seeing gods and ghosts. C、Their extraordinary sensitivity and sen

The dog has always been considered man’s best friend. Always noted for being particularly faithful in watching over children, he also has his place by the fireside, in the cow pasture, on the sheep range, and beside the hunter in forest or the blind. He is easy to train, works hard, and often performs astonishing feats.(26)And in the frozen polar regions he was once the principal motive power, before being largely displaced by the plane and helicopter.
    Because he howls in the presence of forthcoming death, the dog was once thought to have supernatural powers and believed to be capable of seeing gods and ghosts invisible to men. Actually, (27)the basis for these beliefs lies in the dog’s sensitivity to people’s feelings and his superior hearing ability and sense of smell, which enable him to detect signs hidden from human observation. His record of saving lives is outstanding, for he often gives warning of fire and other dangers not noticed by his master.
    The dog’s major contribution, however, has been to medical research. Both his diet and his structure are comparable to those of the human being, and so he has been the subject of countless demonstrations and experiments. Open heart surgery has been made possible largely because of the dog. But his sacrifice has repaid his own species as well by safeguarding it from rabies, distemper, and other diseases.
26. Q: According to the article, what were dogs once used to do in the polar regions?
27. Q: What actually makes dogs have so-called supernatural powers?
28. Q: What do we know about dog’s major contribution?