数列$\left\{a_n\right\}$为各项为正数的等比数列，且$a_4=2$已知函数$f\left(x\right)={\log }_{\frac{1}{2}}x$，则$f\left({a_1}^3\right)+f\left({a_2}^3\right)+\cdots +f\left({a_7}^3\right)=( \; )$

硬水中含有较多的可溶性钙和镁的化合物，会给生活和生产带来许多影响。下列软化硬水程度最高的方法是（        ）

阅读下面短文, 按照句子结构的语法性和上下文连贯的要求, 在空格处填入一个适当的词或使用括号中词语的正确形式填空。

      About the importance of health, nobody can explain ____ (well) than your doctor. They are the people who really know the importance of keeping fit and healthy. Every time I put on ____ extra pound, my doctor will remind me about what is happening ____ my body. We may look healthy but we don't know ____ (clear) what is happening inside. And there are many different ways we can make sure that we are as ____ (health) inside as we are outside. The first and easiest step is keeping a good ____ balanced diet. Next is sleeping well. Sleep early. Make sure you get your nine hours' sleep. Do not skip your breakfast. It is one of the most important ____ (meal) of the day. Exercise every day. Go for a swim, or walk, or just play football or tennis. Try your best not to have too much stress because it''s very ____ (harm) to your health. Remember to keep ____ (wash) your hands, and then you won't catch any infections(传染病). And getting away from your bad habits ____ (be) important too.