Couple of Other Economics Questions - Quickies once again

[aditya]

OK. So I put E on my test for 1, and the teacher said that A was the correct answer. I can see how C is the correct answer as in PPF, it your going from one to another, the opportunity cost of producing one increases as you move along the graph (if that made any sense.)

But I still think that E makes the most sense, meh I guess I have to talk to professor about it.