The correct option is C heating, cooling, cooling, heating
K→L⇒ Isobaric process, V is increasing with increase in temperature according to Charle's law ⇒Heating
L→M⇒ Isochoric process, P is decreasing with decreasing temperature according to Gay lussac's law ⇒Cooling
M→N⇒ Isobaric process, V is decreasing with decrease in temperature according to Charle's law ⇒Cooling
N→K⇒ Isochoric process, P is increasing with increasing temperature according to Gay lussac's law ⇒Heating