Many airlines now allow passengers to print their boarding passes online ______ their valuable time.
A:save
B:saving
C:to save
D:saved
生物的主要遗传物质、遗传物质的主要载体、遗传物质主要存在部位依次是( )
一汽车以10m/s的速度向一山崖行驶,司机经过某处鸣笛时,3s后听到回声,求鸣笛处距山崖的距离?(当时声速为340m/s)