But protecting plants and trees in the garden may not be too difficult if you follow a few suggestions.

VOA: special.2010.01.12

Generally, you think about the immune system protecting against different classes of pathogens and several classes of pathogens are shown on this table.

大体上,你们会认为免疫系统使,我们免受不同种类病原体的侵害,这个表格里介绍了几类病原体

耶鲁公开课 - 生物医学工程探索课程节选