A:K+、Na+、HCO3﹣、SO42﹣
B:Na+、Fe3+、I﹣、Cl﹣
C:Na+、NH4+、NO3﹣、Cl﹣
D:Na+、Ba2+、SO42﹣、NO3﹣
分类法是化学学习和研究的重要方法之一.下列分类正确的是( )
I _________ little time to get ready for the test, so I wasn't confident at that time.