Which of the following compounds has the highest boiling point?

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

Given below are two statements :
Statement $I$ : $S_N2$ reactions are 'stereospecific',indicating that they result in the formation of only one stereo-isomer as the product.
Statement $II$ : $S_N1$ reactions generally result in the formation of product as racemic mixtures.
In the light of the above statements,choose the correct answer from the options given below :

Rate of $S_N2$ reactions depends on :

The major products $X$ and $Y$ respectively from the following reactions are:

The compound having the longest $C-Cl$ bond is: