>>98
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
h#define SEL 4

int main(void)
{
char s[] = "ABCDEF", tmp;
int i, j, lth = 0;

srand(time(NULL));
while (s[lth])
lth++;
for (i = 0; i < SEL; i++) {
j = rand() % (lth - i) + i;
tmp = s[j];
s[j] = s[i];
s[i] = tmp;
}
s[i] = '\0';
printf("%s\n", s);

return 0;
}