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單項(xiàng)選擇題

You use Microsoft .NET Framework 4 to create a Windows Presentation Foundation (WPF) application. 
You write the following code fragment. (Line numbers are included for reference only.)

You need to ensure that a video file begins to play only when a user clicks Play. 
Which code fragment should you insert at line 06?()

A.
B.
C.
D.

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