Final answer:
The Green Knight arrives at King Arthur's court in the middle of a New Year's Eve feast.
Step-by-step explanation:
The statement that should be included in a summary of the first section of Sir Gawain and the Green Knight is option B: The Green Knight arrives at King Arthur's court in the middle of a New Year's Eve feast.
This statement is important because it introduces the main conflict of the story, which is the challenge issued by the Green Knight. The arrival of the Green Knight disrupts the festive atmosphere and creates tension among the characters.