A:只闭合开关S2,电吹风吹出热风
B:只闭合开关S1,电吹风吹出冷风
C:同时闭合开关S1、S2,电吹风吹出冷风
D:同时闭合开关S1、S2,电吹风吹出热风
下列物质中,既含有离子键又含有非极性共价键的是( )
—What a lovely card! Where did you buy it?—I made it by _______.