Three Carnot engines E1 E2, E3; operate as shown in the figure (T1 > T2 > T3).The efficiency of the engine E3 in terms of the efficiencies η1 and η2 of the engines E1 and E2respectively, is

• A. η1 + η2
• B. η1 + η2 - η1η2
• C. 1 - η1 - η2
• D. 1 - η1η2