Major Field Test Sample Questions (need further clarification)
I will try my best to explain the first question. 

They are basically asking what value pos need to be in order for the stack to be empty. Since we are using an array as a stack, we have a choice between 0 or N-1. Looking at the code, Pop increment pos and push decrement pos. We want to follow pop because it pops the first element and so on to the last element. If we pop all elements in the array it will equal N-1 values. The answer should be D.