下列程序执行之后，将输出 public class exl9 { public static void main(string[] args) { int x=3; int y=7; switch(y/x){ case 1: y*=2; break; case 2: y*=3; break; case 3: y*=4; break;default: y=0; } System.out.print(y); }}

A．28

B．21

C．14

D．0