$A$ red coloured mixed oxide $(X)$ on treatment with conc. $HNO_3$ gives a compound $(Y).$ $(Y)$ with $HCl$ produces a chloride compound $(Z)$ which can also be produced by treating $(X)$ with conc. $HCl.$ Compounds $(X),$ $(Y),$ and $(Z)$ will be

The correct statements among the following are:
$(A)$ $BeH_2$ and $MgH_2$ are polymeric in nature.
$(B)$ $LiH$ is unreactive to oxygen at moderate temperatures.
$(C)$ $BeH_2$ and $MgH_2$ possess significant covalent character.
$(D)$ The stability of alkali metal hydrides follows the order $LiH < NaH < KH < RbH < CsH$.

There are four identical containers,initially evacuated,and equal moles of the mentioned compounds are taken in each container (as shown in the diagram). The temperature is kept at $500 \ ^oC$ in each container,which are connected to a manometer. If the heights of the $Hg$ column recorded in the manometers are $x_1, x_2, x_3,$ and $x_4$ respectively,then the relation between $x_1, x_2, x_3,$ and $x_4$ is:

'Bordeaux mixture' is used as a fungicide. It is a mixture of

The compound which gives off oxygen on moderate heating is

Holme's signals can be obtained by using