如果抽样总体中存在周期性的波动和变化，为了保证样本的代表性，研究者应该避免采用的取样方式是

Although the trffic is not busy, he likes to drive at a_______ speed.

陈鹤琴“活教育”教学的四个步骤是实验观察、阅读思考、创作发表和()

In order to increase our output, we need to import more production _______.

为了探讨家庭教育与儿童身心发展之间的关系，某学说提出了“家庭教育方式与儿童身心发展相关”的研究假设，这种假设属于

设来自总体的简单随机样本，记则下列结论中不正确的是（）.

某公司进行办公室装修，若甲乙两个装修公司合做，需10周完成，工时费为100万甲公司单独做6周后由乙公司接着做18周完成，工时费为96万元，甲公司每周的工时（）

What he said in the meeting _______ everybody present.

Sometimes it is very difficult to _______ some of the English words. Even the native speaker can not help.

Free medical service is _______ to nearly all the college students in China.