1.0) a[XXX] //XXX indicates Pending to BE Evaluated
Now Here, a[XXX] is still refer to original int a.
Now you go from to of the Stack.
so, First array a will refers to array c. Please note that this is on a stack only.
Then it will see for the fourth element(Index : 3) in array a. (You can say array c). Now the third element in a or say c is 40. So it will finally try to find out value of a. And you already know, this is wrong index since it can point to max index 3.