漂白液的主要成分是NaClO，NaClO中氯元素的化合价是（  ）

用方框中所给单词的适当形式填空。

         As we know, there are many beautiful places in China, such as Hong Kong, Harbin. They attract a lot of people at home and abroad. But it's hard for ____ to choose where they can go. You can tell them ____ Guide to China, which ____ China in detail. If they have no chance to go through the book, you may show them advertisements for traveling, then after ____, they can decide where to go. They will have a good trip and take photos in ____ of it.

①羌笛何须怨杨柳，春风不度玉门关    ②人间四月芳菲尽，山寺桃花始盛开

③莫恋南国春色好，燕地梅花胜桃红    ④溪云初起日沉阁，山雨欲来风满楼

制作植物临时装片第一次滴加的是清水而制作动物临时装片滴加的是____，起到的作用是____，染色用的都是____，其中染色最深的部位是____，补充制作动物临时装片的步骤：擦，滴，____，____，盖，____，____．