$n-$propyl bromide on treating with alcoholic $KOH$ produces

The least reactive alkyl chloride in an $S_N2$ reaction is:

For the following reactions,which of the following statements is correct?
$A. \, CH_3CH_2CH_2Br + KOH \rightarrow CH_3CH=CH_2 + KBr + H_2O$
$B. \, (CH_3)_2CHBr + KOH \rightarrow (CH_3)_2CHOH + KBr$
$C. \, C_6H_{10} + Br_2 \rightarrow C_6H_{10}Br_2$

What would be the product formed when $1-Bromo-3-chloro$ cyclobutane reacts with two equivalents of metallic sodium in ether?

$KCN$ reacts readily to give a cyanide with:

Which of the following cannot undergo $E_2$ reaction?