Engineering Thermodynamics
A closed system is one in which

Neither mass nor energy crosses the boundaries of the system
Both energy and mass cross the boundaries of the system
Mass does not cross boundaries of the system, though energy may do so
Mass crosses the boundary but not the energy

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Engineering Thermodynamics
According to Dalton's law, the total pressure of the mixture of gases is equal to

Greater of the partial pressures of all
Sum of the partial pressures of all divided by average molecular weight
Average of the partial pressures of all
Sum of the partial pressures of all

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