Answer:
People seated in an auditorium
Step-by-step explanation:
The arrangement of particles in a solid are fixed, vibrations still occur because they have internal energy, however they cannot move freely due to the intermolecular forces that hold them together.
Bricks cemented together in a wall: This model is not the most accurate, because yes the particles are in a fixed position, but the bricks do not show the vibrations of the molecules.
Beads moving around in a rattle: This model would rather represent gas molecules, because they move freely.
People seated in an auditorium: This is the most accurate, because even though they are seated in a "fixed" position, they can still "vibrate" (they can turn and talk to the people on either side of them. They are never completely still).
Students walking through a crowded hall: This model would rather represent liquid molecules, because they are not fixed in one position, but they are not running around either (like gas molecules).