Which of the following is not an ore of magnesium?

If $\alpha, \beta, \gamma$ are the roots of the equation $x^3-6x^2+11x-6=0$ and if $a=\alpha^2+\beta^2+\gamma^2$,$b=\alpha\beta+\beta\gamma+\gamma\alpha$ and $c=(\alpha+\beta)(\beta+\gamma)(\gamma+\alpha)$,then the correct inequality among the following is

If $p$-th,$q$-th,and $r$-th terms of a geometric progression are the positive numbers $a, b,$ and $c$ respectively,then the angle between the vectors $(\log a^2) i + (\log b^2) j + (\log c^2) k$ and $(q-r) i + (r-p) j + (p-q) k$ is

The five-kingdom classification system was proposed by whom?

If the line $y=2x+c$ is a tangent to the circle $x^2+y^2=5$,then a value of $c$ is

The complete set of values of $x$ for which the function $f(x) = 2 \log_e(x-2) - x^2 + 4x + 1$ is increasing is: