阅读对人成长的影响是巨大的，一本好书往往能改变人的一生，每年的4月23日被联合国教科文组织确定为“世界读书日”．某校本学年开展了读书活动，在这次活动中，八年级（1）班40名学生读书册数的情况如表：

根据表中的数据，求：

①汉武帝时设刺史

②刺史最初主要监察地方政治

③该制度削弱了相权，加强了皇权

④州在东汉后期演变为郡县之上的高一级地方机构

    Do you know Chen Yixun? He is a great singer from Hong Kong. He has a lot of beautiful songs, so many people love him. This year Chen Yixun gives concerts (演唱会) in some cities in China. And on November 7 the concert is in Jiaxing.

    Chen Yixun wants to give great concerts, and he does a lot of work for that. First, he practises singing every day. And he always drinks warm water. There are also dances at the concerts, so he needs to practice dancing, too. It's a hard job. Then, he also needs to do exercise like running and swimming. He has to be healthy and strong for the concerts.

    “I have a busy life, but I love it. I enjoy singing and I wish to give great shows to people,” says Chen Yixun. Wish him good luck!

如图表示“制作洋葱鳞片叶表皮细胞临时装片”部分操作步骤，步骤②和④滴加的液体分别是（  ）