变压器效率与变压器负荷和损耗有关负载率在（）时效率最高。
A.0.3～0.5
B.0.5～0.6
C.0.6～0.7
D.0.7～0.8
参考答案：B
Only when possible to settle the problem.[ ]
A. does the editor come will it be
B. the editor comes will it be
C. has the editor come it will be
D. the editor comes it will be
命令LEN(“THIS IS MY BOOK”)的结果是 【7】 。
