也可以直接用介词 to代替and。例如：
3. The incubation period is most frequently between 7 to 21 days.
孵化期大多为7到21天。
七、And用在强调结构中
1、用and连接同一个形容词的比较级，表示发展和程度的变化：
1）The patient is getting worse and worse.
患者的病情在不断恶化。
2）The power output becomes lower and lower by overloading.
超负荷造成功率输出越来越低。
2、用and连接同义词。例如：
1）We completely and totally agree to the project put forward by them.
我们完全同意他们提出的方案。
2）The end and aim of the book is explained in the preface.
本书的宗旨在前言中作了说明。
3、有时用and重复整个句子，也是为了起加强语气的作用。如：
We need to know and we need to know as much as possible in order to adapt to the sort of changes in all aspects of science that will fall upon us like a tidal wave.
为了适应各个科学领域发生的巨大变化，，我们需要大量的知识。
（华南师范大学外文学院通讯员郑世炳供稿 摘自我翻我译 翻译论坛）