程序运行时不能输入运算符

输入运算符那块不运行

#include <stdio.h>
int main()
{
double a, b, c, d, r, i, t;
char op;

printf("输入第一个数的实部和虚部");
scanf_s("%lf%lf", &a, &b);
printf("输入第二个数的实部和虚部");
scanf_s("%lf%lf", &c, &d);
printf("输入运算符");
scanf_s("%c", &op, sizeof(op));


switch (op)
{
case '+':
	r = a + b;
	i = b + d;
	break;
case '-':
	r = a - b;
	i = b - d;
	break;
case'*':
	r = a * b - c * d;
	i = a * d + b * c;
	break;
case'/':
	t = c * c - d * d;
	if (t == 0)
	{
		printf("The denominator is 0.\n");
		return 0;
	}
	r = (a * c + b * d) / t;
	i = (a * d - b * c) / t;
	break;
default:
	printf("Invalidation operator.\n");
	return 0;
}
printf("The result is %lf+%lf\n", r, i);

}