Consider the following C program:

void fun(void) {

int a, b, c; /* definition 1 */ .. .

while (. . .) {

int b, c, d; /*definition 2 */ . . . <------------- 1

while (. . .) {

int c, d, e; /* definition 3 */ . . . <------------- 2

}

. . . <-------------- 3 }

. . . <---------------- 4 }

For each of the four marked points in this function, list each visible variable, along with the number of the definition statement that defines it.