18. Which of the following statement about the Carnot engine is not correct:
(A) The efficiency of a Carnot engine operating between temperatures T₁ and T₂ (T₁＞T₂) is 1 − .
(B) Carnot engine has the best efficiency for given two heat reservoirs.
(C) The entropy of a Carnot engine during a cycle remains constant.
(D) The efficiency of any reversible engine is identical to that of a Carnot engine for given two heat reservoirs.