Answer:
Step-by-step explanation:
An open system is defined as the a system in which energy or mass can be gained or loss from the environment.
Here in this case a wood burning fireplace represents an open system as it is directly taking oxygen from the atmosphere.
During this direct exchange of gases heat is produced hence mass of wood is lost and oxygen is gained from the atmosphere.
So as fire is required from atmosphere to burn the wood, it best explains why a wood burning represent an open system.