發送短信 : Student's conceptual frameworks in mechanics

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| || | ||   / _ \\  | \  / ||  /_   _//  |  _ \\  
| || | ||  | / \ || |  \/  ||   -| ||-   | |_| || 
| \\_/ ||  | \_/ || | .  . ||   _| ||_   | .  //  
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  `---`     `---`   `-`  `-`   `-----`   `-` --`