Absorption refrigeration (ideal/Carnot): expression for C.O.P. Let T1 = generator (heat source) temperature, T2 = condenser/absorber (heat sink) temperature, T3 = evaporator (refrigerated space) temperature, all in absolute units (K). Select the correct ideal C.O.P. formula for an absorption refrigerator.

Concept/Approach
An ideal absorption refrigerator can be modeled as a combination of a heat-driven heat pump (generator/absorber loop operating between T1 and T2) powering a refrigeration cycle (evaporator/condenser between T3 and T2). The maximum (Carnot) C.O.P. is the product of the Carnot C.O.P. of the refrigerator and the efficiency of the heat-to-work conversion analogue.

Derivation sketch
Carnot refrigerator between T3 (cold) and T2 (sink): COP_ref = T3/(T2 − T3).Carnot heat engine analogue between T1 (source) and T2 (sink): η_Carnot = (T1 − T2)/T1.For a heat-driven refrigerator, the effective COP (per unit heat at T1) = COP_ref × η_Carnot = (T3/(T2 − T3)) × ((T1 − T2)/T1).

Option check
B matches the ideal expression.
Other options either omit the driving-temperature factor or misplace temperatures.

Final Answer
COP = (T3/(T2 − T3)) × ((T1 − T2)/T1).