prevent 通常会接所有格形容词 动名词或接受词 from 动名词。当主词没有必要列出时，prevent 可以直接接动名词，也可以接名词。
举例
- you can't prevent my leaving.
- you can't prevent me from leaving.
- i want to prevent his getting sick.
- i want to prevent him from getting sick.
- this campaign is designed to prevent drowning.
- preventing stealing is our main goal this year.
- we are working to prevent forest fires.
- this vaccine will prevent malaria.