Answer:
B). Jem Finch
Step-by-step explanation:
'To Kill A Mocking Bird' authored by Harper Lee explores the key idea of 'moral human nature and the coexistence of virtue and evil at the same time.'
As per the question, the character who was most likely to be 'sullen and gloomy' at the trial would be Jem finch as he is quite innocent and considers the world and all the people surrounding him to be naturally good but his ideals and beliefs are shaken by the cruelty and evil that he witnesses at the trial. The injustice and hatred that he encounters during the trial badly affects his ideals and eventually he gains an adult perspective of the world that not all people are naturally good and human. This shift makes his transition from childhood to adulthood. Thus, option B is the correct answer.