I do not agree that the answer is right.

Think it is supposed to be 0.

the standard deviation s (sigma) is the square root of the average value of (X - µ)2.

Which means s = sqrt(((1-1)^2)/1) = 0

Or in other words std. deviation equals sqrt of (population-avarage) sq / number of population values

Please correct me if im wrong on the formula it has been a while since i used my statistics 😀