Which of the following will react with a halogen acid at the slowest rate?

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

Identify the correct order for the given property for the following compounds. Choose the correct answer from the options given below:
$(A)$ Boiling Point: $CH_3CH_2Cl < CH_3CH_2CH_2Cl < CH_3CH_2CH_2CH_2Cl$
$(B)$ Density: $CH_3CH_2Br < CH_3CH_2Cl < CH_3CH_2I$
$(C)$ Boiling Point: $CH_3CH_2Br < (CH_3)_2CHBr < (CH_3)_3CBr$
$(D)$ Density: $CH_3CH(I)Br < CH_3CH_2CH_2Br < CH_3CH(Br)Cl$
$(E)$ Boiling Point: $CH_3CH_2CH_2CH_2Cl > (CH_3)_2CHCH_2Cl > (CH_3)_3CCl$

$A$ primary alkyl halide $(a)$ with molecular formula $C_{4}H_{9}Br$ reacts with alcoholic $KOH$ to give compound $(b)$. Compound $(b)$ reacts with $HBr$ to give compound $(c)$,which is an isomer of $(a)$. When $(a)$ reacts with sodium metal,it gives compound $(d)$ with molecular formula $C_{8}H_{18}$,which is different from the compound formed when $n$-butyl bromide reacts with sodium. Identify the structural formula of $(a)$ and write the equations for all the reactions.

Which of the following is the correct order of boiling points for alkyl halides?

Which of the following compounds will undergo $S_{N^1}$ reaction most easily?