To find:
What kind of a system is an aquarium?
Step-by-step explanation:
An open system is a system where the energy and matter of the system are exchanged between the surrounding.
A closed system is a system where the exchange of energy takes place with the surrounding.
An isolated system is where neither energy nor matter of the system is exchanged with the surrounding.
An aquarium is usually made of glass. The temperature inside the aquarium varies in accordance with the temperature of its surrounding. That is the heat energy is exchanged between the system and the surrounding. The oxygen is supplied to the aquarium from the surrounding. That is, the matter is exchanged between the system and surroundings.
Thus aquarium is an open system.
Final answer:
The aquarium is an open system.
Therefore the correct answer is option A.