人体内完整的消化管从上到下依次是（　　）

A．口腔→咽→食管→胃→小肠→大肠→肛门

B．食管→胃→小肠→大肠→肛门

C．口腔→咽→食管→胃→小肠→肛门

D．咽→食管→胃→小肠→大肠→肛门

本题是一个Applet，页面上有一个按钮“请单击”，单击该按钮后弹出一个对话框，对话框上有三个按钮“橙色”、“蓝色”和“红色”，单击其中任意一个按钮，则可以将对话框的背景色设置为按钮名称所对应的颜色。
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class java2 extends JApplet

private JFrame frame;
______()

frame=new JFrame();
frame.setTitle("java2");
frame.setSize(300,200);
frame.getContentPane().add(new ButtonPanel());
JButton PopButton=new JButton("请单击");
getContentPane().add(PopButton);
PopButton.addActionListener(new ActionListener()

public void actionPerformed(ActionEvent evt)

if(frame.isVisible())frame.setVisible(false);
else______;

);


class ButtonPanel extends JPanel

private class ColorAction implements ActionListener

private Color backgroundColor;
public void actionPerformed(ActionEvent actionevent)

setBackground(backgrOundColor);
repaint();

public ColorAction(Color color)

backgroundColor=color;


public ButtonPanel()

JButton jbutton=new JButton("橙色");
JButton jbutton1=new JButton("蓝色");
JButton jbutton2=new JButton("红色");
add(jbutton);
add(jbutton1);
add(jbutton2);
ColorAction coloraction=new ColorAction(Color.orange);
ColorAction coloraction1=new ColorAction(Color.blue);
ColorAction coloraction2=new ColorAction(Color.red);
jbutton.addActionListener(coloraction);
jbutton1.addActionListener(coloraction1);
jbutton2.addActionListener(coloraction2);