Hot coffee is poured into a cylindrical container until it is nearly full. The container is immediately sealed by stretching a rubber balloon across the container mouth and tightly sealing the edges. Twenty minutes later, you observe that the still intact rubber seal

has bulged outward in the center of the mouth of the container.

is still flat across the entire mouth of the container.

has bulged outward only at the edges of the container mouth.

has sagged inward toward the coffee.