Assertion: $S{{F}_{6}}$ exists but $S{{H}_{6}}$ does not.
Reason: $d\pi -p\pi $ bonding cannot take place in $S{{H}_{6}}$.
A.Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
B.Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
C.Assertion is correct but Reason is incorrect
D.Assertion is incorrect but Reason is correct.

Hint: To solve this question first we have to predict the geometry of the compound. $S{{F}_{6}}$ has six electrons in the bond pair and no electrons or lone pair on the central atom which is the sulphur atom. The shape of $S{{F}_{6}}$ molecule is octahedral.

Complete answer:
Assertion: $S{{F}_{6}}$ exists but $S{{H}_{6}}$ does not.
We know that fluorine is the strongest oxidising agent and hydrogen is the weakest oxidising agent. In $S{{F}_{6}}$ fluorine oxidises sulphur to its maximum oxidation state which is +6 and this leads to the formation of $S{{F}_{6}}$. This molecule is octahedral in shape.
Hydrogen is a very weak oxidizing agent as compared to fluorine this means that hydrogen is not able to oxidise sulphur to its maximum oxidation state. Hence, $S{{H}_{6}}$ does not exist. And also, we can say that sulphur is more electropositive than fluorine but sulphur is less electropositive than hydrogen. Hence the only compound possible with hydrogen is ${{H}_{2}}S$ and $S{{H}_{6}}$.

Reason: $d\pi -p\pi $ bonding cannot take place in $S{{H}_{6}}$.
Hydrogen is a very weak oxidising agent and the stable octahedral configuration is only for $S{{X}_{6}}$ molecules containing electronegative ligand atoms like fluorine.

Hence the correct answer is option (B) i.e. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion.

Note:
To solve this type of question, we should first check both the assertion and reason separately because it might be possible that the reason is correct but the assertion is incorrect. only after this we will find the relation between them.