A.
switch(op){ case '+': printf("%d\n", value1 + value2); break; case '-': printf("%d\n", value1 - value2); break; case '*': printf("%d\n", value1 * value2); break; default: printf("Error\n"); break; }
B.
switch(op){ default: printf("Error\n"); break; case '*': printf("%d\n", value1 * value2); break; case '-': printf("%d\n", value1 - value2); break; case '+': printf("%d\n", value1 + value2); break; }
C.
if(op != '+' && op != '-' && op != '*'){ printf("Error\n"); }else{ switch(op){ case '+': printf("%d\n", value1 + value2); break; case '-': printf("%d\n", value1 - value2); break; case '*': printf("%d\n", value1 * value2); break; } }
D.
switch(op){ case '+': printf("%d\n", value1 + value2); break; case '-': printf("%d\n", value1 - value2); break; case '*': printf("%d\n", value1 * value2); break; }