What is the decreasing order of nucleophilicity for the following nucleophiles?
$A = CH_3COO^-$
$B = CH_3O^-$
$C = CN^-$
$D = CH_3-C_6H_4-SO_3^-$

For the following compounds,the correct statement$(s)$ with respect to nucleophilic substitution reactions is(are):
$I$: Benzyl bromide $(C_6H_5CH_2Br)$
$II$: Cyclohexylmethyl bromide $(C_6H_{11}CH_2Br)$
$III$: tert-Butyl bromide $((CH_3)_3CBr)$
$IV$: $1-$Phenylethyl bromide $(C_6H_5CH(CH_3)Br)$
$A$. $I$ and $III$ follow $S_{N}1$ mechanism
$B$. $I$ and $II$ follow $S_{N}2$ mechanism
$C$. Compound $IV$ undergoes inversion of configuration
$D$. The order of reactivity for $I$,$III$ and $IV$ is: $IV > I > III$

The correct order of boiling points of alkyl halides is:

Why is it necessary to avoid even traces of moisture during the use of a Grignard reagent?

The major product $(A)$ is:

Given below are two statements $:$
Statement $(I) :$ $cis-1,2-dichloroethene$ is more polar than $cis-1,2-dibromoethene$.
Statement $(II) :$ Boiling point of $trans-1,2-dibromoethene$ is lower than $cis-1,2-dibromoethene$ but it is more polar than $cis-1,2-dibromoethene$.
In the light of the above statements,choose the most appropriate answer from the options given below $:$