其实，人体就是一个活生生的例子。通常大家都认为细菌是有害的，孰不知人体如果没有了细菌，人是无法存活的。
It is generally believed that viruses are harmful, but scarcely does it come into our mind that a person cannot survive without them.
其实，人体就是一个活生生的例子。通常大家都认为细菌是有害的，孰不知人体如果没有了细菌，人是无法存活的。
It is generally believed that viruses are harmful, but scarcely does it come into our mind that a person cannot survive without them.
