不必
例：
Nature ,time ,and patience are the three great physicians .
大自然、时间、耐心是三个伟大的医师.
Farmers use different kinds of soil conservation methods to protect their land from damage by farming and the forces of nature .
农民运用不同种类的土壤保存方法来保护他们的土地以防止耕种和自然力量的破坏.