Which direction does thermal energy flow in the following diagram?

A hand holding an ice cream cone.
Heat flows from the ice cream to the hand.
Heat flows from the hand to the ice cream.
The system is in a state of equilibrium.
The system is too cold for heat to move.

The chemical bubbles

The population of unionid mussels decreased after zebra mussels were introduced. zebra mussels competed with the unionid mussels for food. the zebra mussels were able to displace the unionid mussels, allowing the zebra mussel population to increase  over the years. the unionid mussel population decreased because  of lack of food.