一架飞机往返于两城之间，顺风需要5小时30分，逆风时需6小时，已知风速是每小时24千米，求两城之间的距离.
3168千米
(80～83题共用备选答案)
胸骨左缘第2、3肋间Ⅱ～Ⅲ级粗糙响亮的连续性杂音，P2亢进( )
A．房间隔缺损B．室间隔缺损C．法洛四联症D．动脉导管未闭E．艾森曼格综合征
一Mr. Johnson, we have found your watch.
一My watch! Thank you. Where _______ it? [ ]
A. do you find
B. have you found
C. did you find
D. were you finding
