Final answer:
The implicit premise of the argument is B) The person speaking did not get any sleep last night, which serves as a supposed justification for leaving work early.
Step-by-step explanation:
The implicit premise in the argument “My boss should let me go home early today. Last night I played an epic 12-hour marathon of Halo” is B) The person speaking did not get any sleep last night. This premise is assumed in the argument because it suggests a reason why the speaker would need to go home early, likely due to exhaustion or lack of rest from playing video games for an extended period. While option C) 'Halo was played for 12 hours' is stated explicitly, the implicit understanding is that the speaker's extended gaming session could have interfered with their rest, thereby justifying the need for leaving work early. Options A), D), and the other examples provided are not directly related to the argument presented.