选择恰当的词语填空，再读一读，记一记。

持续  勤恳  清白  纯洁  宽广  谦逊

挺拔  刚强  清澈  坚贞

①心灵，应该像清泉那样____。

②信仰，应该像玉石那样____。

③人格，应该像松柏那样____。

④意志，应该像钢铁那样____。

⑤气质，应该像梅花那样____。

⑥胸怀，应该像大海那样____。

⑦品德，应该像雪花那样____。

     A good way to pass an exam is to work hard every day in a year. You may fail in an exam if you are lazy for most of the year and then work hard only a few days before the exam. If you want to be good at English, you have to read stories in English, and to speak English as much as possible. A few days before the exam you should go to bed early. Do not go to bed late at night. Before you start answering in the exam, read carefully over the question papers, and try to understand the meaning of each question. When you have finished your exam, read over your answers. Correct the mistakes and be sure that you don't miss anything out.

小明在实验室测量盐水密度。小明先将盐水倒入量筒，如图甲所示，则盐水的体积为____ cm³。接着小明用天平测出空烧杯的质量为20g，然后他将量筒中的盐水全部倒入烧杯，用天平测量烧杯和盐水的总质量，天平平衡时的情景如图乙所示，则烧杯和盐水的总质量为____ g。请你根据以上实验数据计算出盐水的密度为____ kg/m³。