Chapter 7 Question 3 Answer:

(4) All of them

This is a bit of a trick question. All the reverse processes are possible, but not spontaneously (i.e. work has to be applied to make them happen). The measure of whether or not a process is reversible is if both the system and the surroundings return to the original state after the forward and reverse process are completed. For these processes it is possible to put the system back to its original state, but it would require the surroundings to give up work.