【查阅资料】①MnO₂+4HCl（浓） $\underset{\_}{\underset{\_}{\Delta }}$ MnCl₂+2H₂O+Cl₂↑，Cl₂（氯气）为黄绿色气体，有刺激性气味．②H₂O₂溶液为无色液体，在常温下能缓慢分解放出极少量氧气，在加热或有催化剂存在的条件下能快速分解出氧气．

【设计实验】在常温下取一定量的H₂O₂溶液，放置一段时间能看到缓慢放出极少量气泡．加入4gMnO₂粉末后，看到迅速放出大量气泡．不再产生气泡后，将反应后的物质过滤，将滤渣洗涤烘干，称得其质量为4g．

【分析与结论】

    A man wanted to buy a hat. So he went to a hat shop and ____ to the assistant, “I'd like to buy a hat, please.” he said. “Can I try it on, please?” “Of course,” the assistant answered and he brought several ____.

    The man tried them on one by one, but he didn't like ____ of them. “This one is too big and this one doesn't look very nice this one must be too cheap. Would you mind ____ a few more hats, please?” “Not at all,” the assistant said. He ____ to the back of the shop and brought some ____ hats. “Let's try this one.” the man said, “No, I'm afraid it's too wide.” “Let's try that one.” “No, I'm afraid it isn't wide ____.” the man said.

    “Would you like to try this one?” the assistant asked.

    “No, it doesn't look very good.” “Shall I bring some more?” the assistant asked. He ____ very happy, but he went to the back of the shop and brought out all the hats. Of course, the man didn't like any of them.

    “Those hats aren't the right size,” the man said. The assistant was very unhappy now. “The hats are all right sir,” he said____, “but I'm afraid your ____ isn't the right size.