A:钠与水:2Na+2H2O=2Na++2OH-+H2↑
B:CaCO3与稀盐酸:CO32-+2H+=CO2↑+H2O
C:AlCl3溶液中加入足量的氨水:Al3++3OH-=Al(OH)3↓
D:FeCl3溶液与Fe反应:Fe3++Fe=2Fe2+
根据句意和汉语注释,在答卷标有题号的横线上,写出单词的正确形式。(1)He seldom____ (回复) to the e-mails his friends send him.(2)Our English teacher has offered us some useful ____ (建议). I think they will help us a lot in our English study.(3)I came here ____ (专门) to invite you to my party.(4)Listening to music can make you forget your ____ (悲伤).
下列地理现象的发生,与地球自转无关的是 ( )
如图,是二次函数 y=ax2+bx+c(a≠0)的图象的一部分,给出下列命题:①a+b+c=0;②b>2a;③ax2+bx+c=0的两根分别为-3和1;④a-2b+c>0.其中正确的命题是 ____.(只要求填写正确命题的序号)