Consider the following C program:#include <stdio.h> int r(){ static int num=7; return num--; } int main(){ for (r();r();r()) printf("%d",r()); return 0; }Which one of the following values will be displayed on execution of the programs?

The function r() uses a static variable num initialized to $7$. Each call to r() returns the current value of num and then decrements it (num--).

Let us trace the for (init; condition; update) loop step by step:

1. Initialization (r()):

   • r() returns $7$, num becomes $6$.

2. First iteration:

   • Condition check (r()): returns $6$ (non-zero/true), num becomes $5$.

   • Loop body (printf("%d", r())\):r() returns $5$, num becomes $4$. Prints 5.

   • Update expression (r()): returns $4$, num becomes $3$.

3. Second iteration:

   • Condition check (r()): returns $3$ (non-zero/true), num becomes $2$.

   • Loop body (printf("%d", r())\):r() returns $2$, num becomes $1$. Prints 2.

   • Update expression (r()): returns $1$, num becomes $0$.

4. Third iteration:

   • Condition check (r()): returns $0$ (zero/false), num becomes $-1$.

   • The loop terminates.

Combining the printed outputs in order yields 52.

Thus, option (B) is correct.