下列物质的使用不涉及化学变化的是（ ）
A．明矾用作净水剂
B．液氯用作致冷剂
C．氢氟酸刻蚀玻璃
D．生石灰作干燥剂
参考答案：B
解析：
My parents ____ inHong Kong. They were born there and have never lived anywhere else. [ ]
A. live
B. lived
C. were living
D. Will live
绝缘材料的电气性能要求主要包括（）。
A.耐热性
B.介质损耗
C.可塑性
D.表面憎水性
E.绝缘电阻
F.绝缘强度
