A:氢氧化钡溶液和稀硫酸反应:Ba2+ + SO42-=BaSO4↓
B:铁与稀硫酸反应: 2Fe + 6H+ =2Fe3+ + 3H2↑
C:稀醋酸加入到氢氧化钡溶液中:H+ + OH-=H2O
D:氯化铝溶液中加入过量氨水:Al3+ + 3NH3·H2O=Al(OH)3↓+ 3 NH4+
根据句意及首字母或汉语提示完成句子
已知1999×△+4×□=9991,且△和□都是自然数,那么□=____ .
⑴How can you get to the school ?____
⑵Happy birthday !____
⑶What's the weather like in summer ?____
⑷May I speak to Mike ?____
⑸Where is your aunt from ?____
A、It's cold .
B、Shenzhen .
C、Thank you .
D、Take bus No.4 .
E、Yes , speaking .