题目

一个开关同时控制电灯发光和电铃发声，则这两个用电器 A．一定是串联接入电路中    B．一定是并联接入电路中 C．可能串联也可能并联接入电路中   D．以上说法都不正确 答案：  C Celia ________ for two hours and feels really tired．So she wants to rest for a while． [　　] A． has been skating B． skates C． skated D． skating