Consider the following C program
int x, y, m, n;
scanf("%d %d", &x, &y);
/* Assume x>0 and y>0*/
m = x; n = y;
while(m != n)
if (m > n)
m = m-n;
n = n-m;
The program computes
$x+y$ using repeated subtraction
$x \mod y$ using repeated subtraction
the greatest common divisor of $x$ and $y$
the least common multiple of $x$ and $y$
It is an algorithm for $\gcd$ computation.
Here, while loop executes until $m=n$.
We can test by taking any two numbers as $m,n$.
Answer will be (C).