A:月季和玫瑰
B:巢蕨和地钱
C:银杏和铁树
D:卷柏和水杉
—You look so tired. What's the matter?—I was so busy that I didn't go to bed 12 o'clock last night.
下列函数中,是二次函数的是( )
(1 )次氯酸的电子式:
(2 )Cl﹣的结构示意图:
(3 )二氧化硅的分子式:SiO2
(4 )CO2的球棍模型示意图:
(5 )熔化时NaHSO4的电离方程式为NaHSO4=Na++HSO4﹣
(6 )乙酸的结构简式:C2H4O2
(7 )质量数为37的氯原子:1737Cl.
将两个异种点电荷间距增大时,下列说法正确的是( )