Oxidation numbers of $P$ in $PO_{4}^{3-}$,of $S$ in $SO_{4}^{2-}$ and that of $Cr$ in $Cr_{2}O_{7}^{2-}$ are respectively

When acetaldehyde is reacted with $LiAlH_4$,what is the product formed?

Let $\vec{p}$ and $\vec{q}$ be the position vectors of points $P$ and $Q$ with respect to the origin $O$,and $|\vec{p}| = p$,$|\vec{q}| = q$. If points $R$ and $S$ divide the line segment $PQ$ internally and externally in the ratio $2:3$ respectively,and if $\vec{OR} \perp \vec{OS}$,then:

$A$ molecule $(X)$ has $(i)$ four sigma bonds formed by the overlap of $sp^2$ and $s$ orbitals,$(ii)$ one sigma bond formed by $sp^2$ and $sp^2$ orbitals,and $(iii)$ one $\pi$ bond formed by $p_z$ and $p_z$ orbitals. Which of the following is $X$?

The equation of the radical axis of the pair of circles $7x^2+7y^2-7x+14y+18=0$ and $4x^2+4y^2-7x+8y+20=0$ is

$\int_2^3 \frac{dx}{x^2-x}$ is equal to