A:Na+、Cu2+、Cl﹣、OH﹣
B:H+、Ca2+、HCO3﹣、NO3﹣
C:Fe2+、H+、SO42﹣、NO3﹣
D:Na+、CO32﹣、OH﹣、K+
地球的平均半径约为6 371 000米,该数字用科学记数法可表示为( )
The doctor had almost lost hope at one point, but the patient finally ______.