串级式电压互感器是指将（）绕组分为几个单元串联而成，目前使用的220KV串级式电压互感器一般分为（）单元。
参考答案：一次；4个
Fred, who had expected how it would go with his daughter, had a great worry ______ his mind.
A．in
B．on
C．with
D．at
凡办理人民币存取款业务的金融机构应无偿为公众兑换残缺、污损人民币，不得拒绝兑换。
A、正确
B、错误
