Final answer:
The correct word to fill in the blank in the sentence is 'heated', which describes a debate that becomes more intense and emotional rather than remaining calm and professional.
Step-by-step explanation:
The vocabulary word that best fills in the blank in the sentence "We could tell, however, when debate became more _________ than professional, but this was from watching lawyers other than our father. I never heard Atticus raise his voice in my life, except to a deaf witness." is A. heated. In the context of debates and discussions, 'heated' implies that the tone became more intense, emotional, or potentially confrontational, which contrasts with a calm and professional demeanor. The excerpts provided describe scenarios where discussions and judicial proceedings become impassioned or lose their formal decorum, suggesting an escalation towards a 'heated' atmosphere. This is a common occurrence in legal settings where the emotional stakes are high, and individuals' convictions and passionate arguments can sometimes supersede professional restraint. "We could tell, however, when debate became more heated than professional, but this was from watching lawyers other than our father. I never heard Atticus raise his voice in my life, except to a deaf witness."b