鱼类生长最迅速时期一般是在？（）
A.幼年时期
B.性成熟以前
C.性成熟之后
D.衰老期
参考答案：B
对220kV及以下电压等级的电气设备，往往用（）代替雷电冲击与操作冲击耐压试验。
There was a big fire in the building last night. ____, all the people were able to escape.
A．Unluckily
B．Fortunately
C．To be sure
D．Above all
