Select the correct statement from the following.

Two oxides of nitrogen,$NO$ and $NO_2$,react together at $253 \ K$ to form a compound of nitrogen $X$. $X$ reacts with water to yield another compound of nitrogen $Y$. The shape of the anion of $Y$ molecule is:

Charge $q$ is uniformly distributed over a thin half ring of radius $R$. The electric field at the centre of the ring is

The line among the following which touches the parabola $y^2=4ax$ is

Two identical short bar magnets,each having magnetic moment $M$,are placed a distance of $2d$ apart with their axes perpendicular to each other in a horizontal plane. The magnetic induction at a point midway between them is:

$\begin{aligned} & A(\alpha, \beta)=\left[\begin{array}{ccc}\cos \alpha & \sin \alpha & 0 \\ -\sin \alpha & \cos \alpha & 0 \\ 0 & 0 & e^\beta\end{array}\right] \\ & \Rightarrow[A(\alpha, \beta)]^{-1}=\end{aligned}$