Which three statements are true about memory buffer allocation by a MySQL Server?

A.
Thread buffers are allocated when a client connects, and are freed when the client
disconnects.

B.
All dynamic buffers that are set with a SET GLOBAL statement immediately get allocated
globally, and are never freed.

C.
Global buffers such as the InnoDB buffer pool are allocated after the server starts, and
are never freed.

D.
User buffers are allocated at server startup and freed when the user is dropped.

E.
Buffers that are needed for certain operation are allocated when the operation starts, and
freed when it ends.