问题：

[多选] Which three statements describe the functionality of the DO_KEY built-in?（）

A . It accepts both a built-in and a key name as argument. 
B . If no key trigger is defined, the specified built-in executes. 
C . Its parameter must be specified in upper case, enclosed in single quotation marks. 
D . It performs the same task as if you pressed the function key associated with the specified argument. 
E . It executes the key trigger that corresponds to the built-in specified as its parameter.&e