Question
Which shows variable valency
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Assertion $A:$ The spin only magnetic moment value for $\left[ Fe ( CN )_6\right]^{3-}$ is $1.74 BM$, whereas for $\left[ Fe \left( H _2 O \right)_6\right]^{3+}$ is $5.92\,BM$.
Reason $R :$ In both complexes, $Fe$ is present in +3 oxidation state.
In the light of the above statements, choose the correct answer from the options given below:

$\mathrm{NaOH}+\mathrm{Cl}_{2} \rightarrow(\mathrm{A})+$ side products
(hot and conc.)
$\mathrm{Ca}(\mathrm{OH})_{2}+\mathrm{Cl}_{2} \rightarrow(\mathrm{B})+$ side products
$(dry)$