Explanation : The postfix equivallent is 2 3 * 4 5 + -.
For evaluating this using stack,starting from the left,we have to scan one by one, if it is an operand push.
If it is an operator, pop it twice,apply operator on the poppedout entries and push the result onto the stack.
If we follow this,we can find configuration in option(d)is not possible
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14: Stack A has the entries a,b,c(with a on top).
Stack B is empty.An entry popped out of stack A can be printed immediately or pushed to stack B.An entry popped out of the stack B can only be printed. In this arrangement, which of the following permutations of a,b,c are not possible?