某黑色固体粉末可能是Fe、FeO、CuO、C中一种或几种．为了探究其成分，小明同学按照如图所示流程进行了实验．

关于该实验有以下说法：

①若溶液甲呈浅绿色，则原黑色固体粉末中一定含有Fe；

②若步骤Ⅱ中无明显现象，则固体乙中最多只能有四种物质；

③若步骤Ⅱ中有气泡产生，则固体乙一定是C；

④若步骤Ⅱ中有红色固体析出，则固体乙中一定无CuO；

⑤固体乙呈红色，则原固体中一定含有Fe和CuO．

以上说法中正确的个数是（　　）

某运动员获得了一枚金牌，拿回家后，为了鉴别金牌是否是纯金制成的，他测出了金牌的质量为12.5g，体积为0.75cm³，问金牌是否是纯金制成的？（ρ_金=19.3×10³kg/m³）

    I love reading. At age 6, I could be found reading Harry Potter, a difficult book for a 6-year-old but I ____(enjoy) it all the same. ____ soon became obvious that spelling for me was not difficult and I had a wide vocabulary. This is one way I benefited ____ reading at such a young age.

    My advice for you as English learners would be to read the English novels ____you have often read in your native language. Reading novels is a great way of ____(improve) your vocabulary and spelling without realising it as you are absorbed（全神贯注的）in the storyline. You know the sorry well, so its ____(usual) easy to follow it in English even if you do not understand every word.

    This is another essential（基本的）point: it's not necessary ____(understand) every word. If you understand the ____(mean) of the sentence, each word is not necessarily important. Quite often, if a word is used several times in a text, you'll gradually get an idea of ____ it means.

    Give it a try. If you like reading yon could open up ____ whole new world of literature.