How to determine whether a system is closed or not?

[influx]

I know the definition of an open/closed system but I am still confused:

1) Why isn't C a closed system?

2) I know that a simple system's state is defined by just 2 properties (when the system is in equilibrium) but how do we eliminate the wrong answers and determine the correct answer in this question?

3) The independent variable = the thing you change (as far as I know) but that doesn't lead me any closer to the correct answer..

Cheers

 

[Chestermiller]

C isn't a closed system because exhaust gases are entering and leaving the car exhaust (piping).