an identifier may start with an underscore

an identifier may end with an underscore

IF is a valid identifier

All of the above

during external variable definition, storage is set aside by the compiler

during external variable declaration, no storage is set aside by the compiler

the use of external variables may make debugging difficult

All of the above

it is binary representation of a character in the extended binary set

it is of integer type wchar_t

end of file is represented by WEOF

All of the above

they provide a way for two way communication between functions

their scope extends from the point of definition through the remainder of the program

if they are not initialized, they will be initialised to zero

All of the above

address is the numeric value associated with a memory location

two variables can have the same address

value of a variable can be an address

All of the above