You use Microsoft .NET Framework 4 to create a Windows Presentation Foundation (WPF) application.  
The application contains a window as shown in the following exhibit.  
You need to define a DockPanel control that fits the window.  
Which code fragment should you use? 
A.
<DockPanel>   
 <Button Content=”Left”/>   
 <Button Content=”Top” DockPanel.Dock=”Top”/>   
 <Button Content=”Bottom” DockPanel.Dock=”Bottom”/>   
 <Button Content=”Center”/>   
 </DockPanel>
B.
<DockPanel>   
 <Button Content=”Top” DockPanel.Dock=”Top”/>   
 <Button Content=”Bottom” DockPanel.Dock=”Bottom”/>   
 <Button Content=”Left”/>   
 <Button Content=”Center”/>   
 </DockPanel> 
C.
<DockPanel>  
<Button Content=”Left”/>  
<Button Content=”Top” DockPanel.Dock=”Top”/>  
<Button Content=”Center”/> 
<Button Content=”Bottom” DockPanel.Dock=”Bottom”/>  
</DockPanel>  
D.
<DockPanel>  
<Button Content=”Top” DockPanel.Dock=”Top”/> 
 <Button Content=”Left”/>  
<Button Content=”Center”/>  
<Button Content=”Bottom” DockPanel.Dock=”Bottom”/> 
 </DockPanel>