You are creating a Windows Forms application by using the .NET Framework 3.5.  You use LINQ expressions to read a list of customers from the following XML file.

You need to obtain a list of names of customers who are 21 years of age or older.  
Which code segment should you use？（）

You are creating a Windows Forms application by using the .NET Framework 3.5.The application stores a list of part numbers in an integer based array as shown in the following code segment （Line numbers are included for reference only）

You need to use a LINQ to Objects query to perform the following tasks： - Obtain a list of duplicate part numbers：
（1）Order the list by part numbers  
（2）Provide the part numbers and the total count of part numbers in the results   
Which code segment should you insert？（）

You are creating a Windows Forms application by using the .NET Framework 3.5. You have implemented the PrintPage event to send the page output to the printer.The users must select the printer and the page range before printing. You need to ensure that users can print the content of the form by clicking the button control.  
Which code segment should you use？（）

You are creating a Windows Forms application for the design of circuit boards and electronic equipment. You use the .NET Framework 3.5 to create the application x that allows designers to preview designs before printing them.The previewed documents must meet the following requirements：  
（1）The graphics and text are displayed clearly.  
（2）The fullscale preview is set as default for the documents.  
（3）The zoom setting of the preview control is adjusted automatically when the form is resized.   
You need to ensure that the requirements are met when the form that contains the custom print preview control is displayed.  
Which code segment should you use？（）