①称取一定量的固体铁氧体磁性材料溶于过量盐酸，接着先后加入双氧水和氢氧化钠溶液，静置24h，过滤

②将沉淀加入反应瓶中，加入过量的氢氟酸溶液，80℃恒温加热24ha

③蒸发多余氢氟酸和水，得淡红色FeF₃凝胶

④在干燥箱中，以100℃预处理6h，最后掺入铁氧体磁性材料混合研磨制得正极材料

据统计，目前我国青少年网民规模已达1.95亿人，手机已经成为青少年上网方式的首选。但青少年在利用手机网络拓宽视野、与人交往的同时，也面临着信息纷繁复杂、网友真假难辨的困扰。青少年在使用手机网络时应该做到（     ）

    Restaurant  owners  have to know how  ____  ( make) food. They also have to know how to make money. Here are some things they ____ (learn) from scientific studies. The color red ____ (make) people hungry. Red also makes customers____ (eat) fast food restaurants, therefore, have red furniture or walls. Soft colors like pink and light blue make people____  ( relax), so they spend more time____ (eat) their meals. Soft lighting____  ( make )people look good, but it makes food look bad. Loud music  makes people want____ (  leave). Hard seats also____ ( make ) customers want to eat quickly and leave. Many restaurants, especially fast food restaurants, use this knowledge ____ (make) customers eat faster.