单选题 选择正确的语句填在下列程序的横线处。 import java.awt.*; import java.awt.event.*; public class ex30 { Frame f; public static void main(String[] args) { ex30 e = new ex30(); e. te st ( ); } public void test() { f = new Frame("ex30"); ______ f.paok(); f.setVisible(true); } class MyWindowListener extends WindowAdapter { public void windowClosing(WindowEvent e) { System.exit(1); } } }