![](https://cos-cdn.shuashuati.com/pipixue-web/2020-1231-2005-12/ti_inject-812ce.png)
many people have heard of the “brain drain”. This is ____ happens ____ people with good skills and a good education move to another country for study or work, often at the expense of their home countries. (1.0分) A. which; when B. what; that C. what; when D. why; when