Hint: Initially, understand the definition of closed system and an open system. Compare the definition of both the systems. Through the definition, you can find which is an example of a closed system and which is an example of an open system.
Complete step by step answer:
In thermodynamics, a closed system is defined as a system which does not exchange matter but it does exchange energy with its surroundings. On the other hand, an open system is defined as a system which can exchange energy as well as matter with its surroundings.
So, we need to see which of the above mentioned objects does not share matter but does share energy.
In case of a cup of tea, exchange of energy and exchange of matter is possible. Hence, it is an example of an open system.
In the case of an air-tight container, as the name implies, exchange of air is not possible. Thus, exchange of matter is not possible. Hence, it is an example of a closed system.
In case of a jug of water, exchange of energy and matter, both are possible. Hence, it is an example of an open system.
Thus, an air-tight container is an example of a closed system.
Hence, the correct answer is option B i.e an air-tight container.
Note: Pump, boiler, etc, are few other examples of open systems. A simple water bottle is also an example of a closed system. There is an isolated system as well. Isolated system can neither exchange energy nor matter with its surroundings. Thermoflask is an example of an isolated system.
