We all know what a brain is.  A doctor will tell you that the brain is the organ of the body in the head. It controls our body's functions, movements, emotions and thoughts. But a brain can mean so much more. A brain can also simply be a smart person,  If a person is called brainy, she is smart and intelligent.  If a family has many children but one of them is super smart, you could say, "She's the brains in the family. " And if you are the brains behind something you are responsible for developing or organizing something.  For example, Bill Gates is the brains behind Microsoft. Brain trust is a group of experts who give advice.  Word experts say the phrase"brain trust" became popular when Franklin D. Roosevelt first ran for president in 1932,  Several professors gave him advice on social and political issues facing the U. S.These professors were called his "brain trust. " These ways we use the word "brain" all make sense. But other ways we use the word are not so easy to understand. For example, to understand the next brain expression, you first need to know the word"drain." As a verb to drain means to remove something by letting it flow away. So a brain drain may sound like a disease where the brain flows out the ears.  But, brain drain is when a country's most educated people leave their countries to live in another. The brains are,sort of,draining out of the country. However,if people are responsible for a great idea,you could say they brainstormed it. Here,brainstorm is not an act of weather.  It is a process of thinking creatively about a complex topic. For example,  business leaders may use brainstorming to create new products, and government leaders may brainstorm to solve problems. If people are brainwashed, it does not mean their brains are nice and clean.  To brainwash means to make someone accept new beliefs by using repeated pressure in a forceful or tricky way. Keep in mind that brainwash is never used in a positive way. According to the text, if you're the CEO of  Bai Du you can be called  _  .
the brains behind Bai Du Bai Du's brain trust the brain drain of Bai Du the organ of Bai Du