My Q :
PLS HELP : IS ZERO A POSITIVE INTEGER : ??? Whats the thumb rule, I am a bit confused over this.
If Yes then ans D, below,is okay otherwise B cannot be eliminated.
Can anyone pls clarify more on the following Q ?
Thanks for your time

If x is a positive integer, which of the following CANNOT be expressed as n^2, where n is an integer?

A. x^5
B. x^2 − 1
C. Sqrt(X^8)
D. x^2 + 1
E. Sqrt(X^5)


[spoiler]D. For each of choices A, B, C, and E, trying the value x = 1 shows that there is one possible value of x for which the expression results in an integer squared:

A) The result is 1, which is the same thing as
12

B) The result is 0, which is the same thing as
02

C) The result is 1, which is the same thing as
12

E) The results is 1, which is the same thing as
12

For D, however, you cannot find a value of x for which
x2+1
will yield a perfect square. If x = 1, the expression yields a 2. If x = 2, the expression yields a 5. As no two squares (other than 0 and 1) are one number apart, D cannot be a perfect square if x is a positive integer.[/spoiler]