下面有关钠与水反应的实验的说法错误的是( )
A:钠的密度小于水
B:钠的熔点高
C:钠的硬度小
D:钠很活泼
The teacher spoke loud and clearly enough to make himself ________ by all his students.
地球表面的某一点位置可以用经纬网来确定,仔细阅读经纬网图,完成下题.