粗盐中除含有不溶性固体杂质外，还含有MgCl₂、CaCl₂等可溶性杂质．要除去粗盐中的MgCl₂、CaCl₂，选用试剂（均过量）及使用顺序正确的是（　　）

气温大致由低纬向高纬____。在山地和丘陵地区，气温随海拔升高而____。大致每升高100米，气温约下降____℃。

根据句意及汉语或首字母提示完成单词

first of all, from now on, hundreds of,

be careful with, at the moment

⑥This kind old man is not rich but he helps ____ poor children.

⑦ You must study hard ____ and be a good boy.

⑧ ____, let me introduce myself to you.

⑨ ____ that glass. Don't break it.

⑩ The children are playing football on the playground ____.

- Your head teacher has set up a Wechat group. Could you tell _______?

- It is more convenient to communicate with our parents.