启备变额定容量（）。
A.45MVA
B.60MVA
C.30MVA
参考答案：B
The film______for ten minutes when we got to the cinema.
A．has alrealy been on
B．has already begun
C．had already been on
D．had already begun
正常运行的变压器应至少每6年测一次绕组变形。（）
