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.