常用抗生素“先锋Ⅵ”为粉末状固体，每瓶含“先锋Ⅵ”0.5g，注射时应配成质量分数不高于20%的溶液，则使用时每瓶至少需加入蒸馏水（　　）

①SiO₂﹣→Na₂SiO₃；②CuSO₄﹣→CuCl₂；③SiO₂﹣→H₂SiO₃ ；④CuO﹣→Cu（OH）₂；⑤Na₂O₂﹣→NaOH．

    This is my desk. Two____  are on it. One is my English book, and the other (另一本) is my math book. You can also see (也能看见)____CDs  on the desk. The CDs are ____. My pencil box is on the desk,____. A pen,____  eraser and a ruler ____  in it. The pen is black, the____  is yellow, and the ruler is white.  ____  is my pencil? Aha, it's under the desk. Is my computer game  ____the desk，too? No, it isn't. Where is it? I can't____it in my room.