$(6)(4)$ What is the best reagent to carryoul this transition,

$($a$)$ HCl in ether

$($b$)HCl$ in water

$($c$)C{l}_2$ in pyridine

$($d$)$ Lice in pentane

$(25)$ Which structure best fits the following mass spectral data$)$

$\backslash$table$[[\frac{m}{2},$Relative$],[43,91],[71,100],[91,38],[162,13]]$

$($a$)$

$($b$)$

$($e$)$

$($d$)$