Answer 1

Akash Kumar
## is used to concatenate two tokens and use that
b##a##r is make the whole thing with "bar" and #define macro is replaced the( r, a, b) with ( bar)
Then in next line CHAOS is replaced with ( bar) so in next calling statement
void CHAOS(){ printf("order"); } is changes into
void bar(){ printf("order"); }
And due to this when bar() function is called inside main() it will return "order"