Which of the following statement is correct ?

Options

A. The presence of reaction speciesin a covered beaker is an example of open system.
B. There is an exchange of energy as well as matter between the system and the surroundings in a closed system.
C. The presence of reactants in a closed vessel made up of copper is an example of a closed system.
D. The presence of reactants in a thermos flask or any other closed insolated vessel isan example of a closed system.

Explanation

To determine which statement is correct regarding thermodynamic systems, we will evaluate each statement one by one:

### Step 1: Evaluate the First Statement
**Statement:** "The presence of reaction species in a covered beaker is an example of an open system."

- **Analysis:** An open system allows both matter and energy to be exchanged with the surroundings. A covered beaker restricts the exchange of matter (as it is covered), even though it may allow energy exchange (like heat). Therefore, this statement is **incorrect**.

### Step 2: Evaluate the Second Statement
**Statement:** "There is an exchange of energy as well as matter between system and surroundings in a closed system."

- **Analysis:** A closed system allows energy exchange (like heat) but does not allow the exchange of matter with the surroundings. Therefore, this statement is **incorrect**.

### Step 3: Evaluate the Third Statement
**Statement:** "The presence of reactant in a closed vessel, which is made of copper, is an example of a closed system."

- **Analysis:** A closed vessel allows energy exchange (like heat) but does not allow matter exchange. Since the vessel is closed, it fits the definition of a closed system. Therefore, this statement is **correct**.

### Step 4: Evaluate the Fourth Statement
**Statement:** "The presence of reactant in a thermos flask, any other closed isolated vessel is an example of a closed system."

- **Analysis:** A thermos flask is designed to be an isolated system, meaning it does not allow the exchange of energy or matter with the surroundings. Therefore, this statement is **incorrect**.

### Conclusion
The correct statement is the third one: "The presence of reactant in a closed vessel, which is made of copper, is an example of a closed system."

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