架空线路编码指一条线路的编码。架空线路编码共8位，其中第二位表示的是：（）
A、电压等级
B、线路码
C、线路区域码
D、流水号
参考答案：A
Kate had a terrible time this summer. Not a day ________ without having some unpleasantness with her sister at home.
A．she spent
B．she had spent
C．did she spend
D．had she spent
脂肪的熔点和膨胀性与脂肪的结构有什么关系？对研究油脂老化有什么作用？
