b
In $VT$ graph
$ab-process\,\,\,:\,\,\,Isobaric,\,\,temperature\,increases.$
$bc\,process\,:\,Adiabatic\,pressure\,decreases.$
$cd\,process\,:\,Isobaric\,volume\,decreases.$
$da\,process\,:\,Adiabatic,\,pressure\,increases.$
The above processes correctly respresented in $P-V$ diagram $(b)$ .