题目热电厂的效率约为( )。A. 30%~40%B. 60%~70%C. 40%~50%D. 80%~90%热电厂的效率约为( )。A. 30%~40%B. 60%~70%C. 40%~50%D. 80%~90%题目解答答案A. 30%~40%