Don, thank you for the reply. In your example I removed the Activity.Finish that was with the StartActivity(B) and pressing the back button in B goes back to A. This is the behavior I want. I am not doing an Activity.finish when I start another activity, but I do an Activity.Finish in the Activity_Pause sub. I inserted the Activity.Finish in the A and B Activity_pause in your example and pressing the back button in B returns to Main.
I guess I need to do some more reading/understanding on the activity as I thought I should finish when going back to release the resources.