Explanation:

- The sentence before blank No.4 describes finding a badge and implies the person is in a hall.

- The options provided are all nouns related to places one might sit or stand in a formal or large gathering area.

1. Stand: Typically implies standing up, not sitting down. It doesn’t fit well in the context of taking a position in the hall.

2. Lounge: This suggests a relaxed area rather than a formal meeting space within a hall.

3. Couch: Implies a comfortable sofa, not likely found in a formal hall seating arrangement.

4. Seat: Implies a position or place to sit, perfectly fitting the context of taking a place in an audience or gathering hall.

- The correct choice to fill in blank No.4 is option:4, seat.