南京到北京的66次快车每晚22：50发车，次日13：50到达，宁京线全长约1156千米，该列车速度是______千米/时．
列车行驶时间：
t=（24h-22h50min）+13h50min=1h10min+13h50min=15h；
s=1156km，
∵v=
，s t
∴列车速度：
v=
=s t
≈77km/h．1156km 15h
故答案为：77．
| 35．Applications put computers to pratical business (1) , but below the (2) it’s the heart of an operating system—the kernel that provides the technical wizardry to juggle multiple program, connect to networks and store (3) . A traditional kernal provides all the functions for applications. The kemal (4) memory, I/O devices and parcels out processor time. The kernel also supports security and fault (5) , which is the ablity to recover automatically when parts of the system fail. |
(2)
A．earth
B．bottom
C．table
D．surface