What are examples for state functions?
Let's say you go to Stonehenge.
You see a big rock there.
You can observe the state of the rock.
But how much work was done to bring the rock there?
How far away did the rock come from? Was it a downhill or uphill journey?  Was the stone dragged, moved with wheels, or pulled on a sled over snow?  

So you can know the exact state of the rock, but not how much work was done to bring it to that state. 

Therefore work is not a state function. The others given in the exercise, i.e. internal energy, pressure, volume, temperature are all state functions.