In which of the following sets are allotropes of carbon correctly matched with their uses?
$i$. graphite - crucibles
$ii$. activated charcoal - water filters
$iii$. carbon black - fuel
The correct answer is

Which of the following is a mixed oxide?

The oxidation state shown by silicon when it combines with strongly electropositive metals is

Given below are two statements:
Statement $I$ : $SiO_2$ and $GeO_2$ are acidic while $SnO$ and $PbO$ are amphoteric in nature.
Statement $II$ : Allotropic forms of carbon are due to property of catenation and $p \pi-d \pi$ bond formation.
In the light of the above statements,choose the most appropriate answer from the options given below:

Reaction of an inorganic sulphite $X$ with dilute $H_{2}SO_{4}$ generates compound $Y$. Reaction of $Y$ with $NaOH$ gives $X$. Further,the reaction of $X$ with $Y$ and water affords compound $Z$. $Y$ and $Z$,respectively,are:

Which of the following statements are correct?
$1.$ Charcoal can be obtained by heating wood in the absence of air.
$2.$ Charcoal is an impure form of graphite.
$3.$ Diamond is thermodynamically the most stable allotrope of carbon.
$4.$ Coke is used as an oxidising agent during the extraction of iron from its ores.