The correct option is B. The statement in option B shows that Policles was mocking the effort of the singer. He compared his singing to that of an ill conditioned dog that is making a discordant sound. This statement shows that Policle considered the musician as one who does not know how to sing at all.
The sentence in the excerpt from Arthur Conan Doyle's "The Contest" that suggests that the author's tone is mocking are: b). The low note was a grunting, a rumble , the deep discordant growling of an ill-conditioned dog. The author is comparing the lyre player to a dog that has been badly trained; C) the lyre sounded quite funny making the singer's voice be heard with difficulty ; and e) the player was nothing but a pretender and ,in the author's opinion, he / she should have been kicked out from stage.