A:人的心脏正常跳动一次的时间约为3s
B:成年人的步行速度约为11m/s
C:中学生的质量约为500kg
D:黑板的长度约为4m
Do you see the sea? The sea is blue,and it is very large(大的).The sea looks beautiful in a sunny day. If(如果)you swim,in the sea,you know that the water is salty(咸的).Do you like the sea?