A:2.1×109
B:0.21×109
C:2.1×108
D:21×107
如图是盐酸滴入氢氧化钠溶液中,有关粒子之间反应的示意图.下列说法错误的是( )
I am looking after little Tom today. He's been in my house _ 8:00 this morning.