#include <stdio.h>

main()
{
    char line[100];
    char decision[100];
    printf("Are you gonna throw it?n");
    printf("Type yes or no.n");

    scanf("%s", line);
    printf("%s n", line);

    if (line == "yes") {
        printf("Thanks.n");
    } else if (line == "no") {
        printf("Why not?n");
    }

    printf("Do you want to do this again?n");
    scanf("%s", decision);
    if (decision == "yes") {
        main();
    };
}

if (strcmp(line, "yes") == 0) {
    printf("Thanks.n");
} else if (strcmp(line, "no") == 0) {
    printf("Why not?n");
}

if (strcmp(line, "yes") == 0) { ... }

if (decision == "yes")
{
     main();
 }; //<-- if you want to keep this code at all

strcmp(decision, "yes"); //returns 0 if they are equil

main() {
  char line[100];
  char decision[100] = "yes";
  while(!strcmp(decision, "yes")){
    printf("Are you gonna throw it?n");
    printf("Type yes or no.n");
    scanf("%s", line);
    printf("%s n", line);
    if (!strcmp(line, "yes"))
      printf("Thanks.n");
    else if (!strcmp(line, "no"))
      printf("Why not?n");

    printf("Do you want to do this again?n");
    scanf("%s", decision);
  } //end while
} //end main