上品是指极优品、优品、佳品的邮品。无任何折痕、污染、退色、短齿等问题，纸张、图案、背胶、齿孔的外观质量均属上乘。
参考答案：对
By using ears one can tell the direction ____ a sound comes.
A．in which
B．from which
C．with which
D．through which
鉴赏姜夔《扬州慢》
