What detail from this passage best suggests that Kafka views music as a source of human nature. His sister began to play; father and mother paid close attention, one on each side, to the movements of her hands. Drawn in by the playing, Gregor had dared to come forward a little and already had his head in the living room. Before, he had taken great pride in how considerate he was but now it hardly occurred to him that he had become so thoughtless about the others. What's more, there was now all the more reason to keep himself hidden as he was covered in the dust that lay everywhere in his room and flew up at the slightest movement; he carried threads, hairs, and remains of food about on his back and sides; he was much too indifferent to everything now to lay on his back and wipe himself on the carpet like he had used to do several times a day. And despite this condition, he was not too shy to move forward a little onto the immaculate floor of the living room.

No-one noticed him, though. The family was totally preoccupied with the violin playing; at first, the three gentlemen had put their hands in their pockets and come up far too close behind the music stand to look at all the notes being played, and they must have disturbed Gregor's sister, but soon, in contrast with the family, they withdrew back to the window with their heads sunk and talking to each other at half volume, and they stayed by the window while Gregor's father observed them anxiously. It really now seemed very obvious that they had expected to hear some beautiful or entertaining violin playing but had been disappointed, that they had had enough of the whole performance and it was only now out of politeness that they allowed their peace to be disturbed. It was especially unnerving, the way they all blew the smoke from their cigarettes upwards from their mouth and noses. Yet Gregor's sister was playing so beautifully. Her face was leant to one side, following the lines of music with a careful and melancholy expression. Gregor crawled a little further forward, keeping his head close to the ground so that he could meet her eyes if the chance came. Was he an animal if music could captivate him so? It seemed to him that he was being shown the way to the unknown nourishment he had been yearning for. He was determined to make his way forward to his sister and tug at her skirt to show her she might come into his room with her violin, as no-one appreciated her playing here as much as he would. He never wanted to let her out of his room, not while he lived, anyway; his shocking appearance should, for once, be of some use to him; he wanted to be at every door of his room at once to hiss and spit at the attackers; his sister should not be forced to stay with him, though, but stay of her own free will; she would sit beside him on the couch with her ear bent down to him while he told her how he had always intended to send her to the conservatory, how he would have told everyone about it last Christmas - had Christmas really come and gone already? - if this misfortune hadn't got in the way, and refuse to let anyone dissuade him from it. On hearing all this, his sister would break out in tears of emotion, and Gregor would climb up to her shoulder and kiss her neck, which, since she had been going out to work, she had kept free without any necklace or collar.

a. "Her face was leant to one side, following the lines of music with a careful and melancholy expression."

b. "Was he an animal if music could captivate him so?"

c. "His sister began to play; father and mother paid close attention, one on each side, to the movements of her hands."

d. "He was determined to make his way forward to his sister and tug at her skirt to show her she might come into his room with her violin"