It seems to be strange to you there is a blind spot(点) on the eyes. Here is an interesting experiment that can make something disappear, when one eye is open.
　Make a card about the size of a postcard and write two English letters L and R on it, L on the left and R on the right. First, hold the card about 80 cm away and you see both the letters. Then close your right eye and look at the letter R only with your left eye. And now, as you move the card slowly towards you, you'll find the letter L disappearing. But if you move the card nearer to your face, the letter will be seen again. Now do the same experiment with your left eye closed, you'll find the letter R disappearing.
    Why does the letter disappear? It is because there is a blind spot on the eye. When the image of the letter falls on the blind spot, it won't be seen. That is why either of the letters disappears.

下列有关盛放某些气体的集气瓶，其摆放情况正确的是（   ）

实验桌上有一架没有砝码的托盘天平、一个量筒、水、两个相同的烧杯、细线、小石块、滴管，请你完成测定小石块密度的实验．

阅读下面的文言文，完成下列各题。

    余懋衡，字持国，婺源人。万历二十年进士。除永新知县。征授御史。时以殿工，矿税使四出，骄横。懋衡上疏言：“与其骚扰里巷，榷及鸡豚，曷若明告天下，稍增田赋，共襄殿工。今避加赋之名，而为竭泽之计，其害十倍于加赋。”忤旨，停俸一年。

    巡按陕西。税监梁永辇私物于畿辅，役人马甚众。懋衡奏之。永大恨使其党乐纲贿膳夫毒懋衡再中毒不死拷膳夫获所予贿及余蛊遂上疏极论永罪言官亦争论永帝皆不省。永虑军民为难，召亡命擐甲自卫。御史王基洪声言永必反，具陈永斩关及杀掠吏民状。巡抚顾其志颇为永讳，永乃藉口辨。帝疑御史言不实。而咸宁、长安二知县持永益急。永党王九功辈多私装，恐为有司所迹，托言永遣，乘马结阵驰去。县隶追及之华阴，相格斗，已皆被系，懋衡遂以反逆闻。永窘甚，爪牙尽亡，独纲在，乃教永诬劾咸宁知县满朝荐，朝荐被逮。永不久亦撤还，关中始靖。懋衡寻以忧归。起掌河南道事。擢大理右寺丞，引疾去。

    天启元年，起历大理左少卿，进右佥都御史，与尚书张世经共理京营戎政。进右副都御史，改兵部右侍郎，俱理戎政。三年八月，廷推南京吏部尚书，以懋衡副李三才；推吏部左侍郎，以曹于汴副冯从吾。帝皆用副者。大学士叶向高等力言不可，弗听。懋衡、于汴亦以资后三才等，力辞新命，引疾归。明年十月，再授前职。懋衡以珰势方张，坚卧不起。既而奸党张讷丑诋讲学诸臣，以懋衡、从吾及孙慎行为首，遂削夺。崇祯初，复其官。

（选自《明史·余懋衡传》）

如图所示，鱼、肉的新鲜度不同，其浸出液pH会发生相应变化．鱼、肉的浸出液pH变大，其新鲜度的变化情况为（   ）