The range of the function $f(x)=-\sqrt{-x^2-6x-5}$ is

Which one of the following is not correct?

The organization of living organisms starts with which level?

Consider three observations $a, b$ and $c$ such that $b = a + c$. If the standard deviation of $a + 2, b + 2, c + 2$ is $d$,then which of the following is true?

Which one of the following statements is incorrect?