Why this prints 3?

Question

#include <stdio.h>

int main() {
int a = (1,2,3);
printf ("%d", a);
return 0;
}

Answer 1

Because it evaluates the last expression and returns it. So the last expression here is "3"

Answer 2

A different behaviour found for C++ assignment operator, without the parentheses, the first value will be taken instead.

(Edit)
Apparently the same behaviour in C language.

https://code.sololearn.com/c3hQ2573ECgC/?ref=app

Answer 3

https://www.sololearn.com/discuss/1672605/?ref=app