[单项选择]按自然资源客观存在条件与特征为标准，可分为( )。
A. 可再生资源与不可再生资源
B. 恒定资源与可再生资源
C. 地下资源和地表资源
D. 以上均不正确

A recent development is the local area network (LAN). (21) its name implies, it serves a local area-possibly as small as a single room, typically an area like an university campus or the premises of a particular business. Local area networks were developed to (22) a need specific to microcomputers the sharing of expensive resources. Microcomputers are cheap, but highcapacity disc stores, fast and/or good quality printers, etc. are expensive. The object of the LAN is to allow (23) microcomputers shared access to these expensive resources, since the microcomputers are cheap, it is a necessary feature of a LAN that the method of connection to the network, and the network hardware (24) , must also be cheap.
A local area network links a number of computers and a number of servers which provide communal facilities, e. g. file storage. (A server usually includes a small microprocessor for control purposes. ) The computers and servers are known as stat
A. a great deal of
B. a lot
C. a number of
D. a bit of

2 小时（含）以内乘务组及时向机组了解延误信息（包括时间，延误原因等）;乘务组应及时对客舱进行广播，每 15 分钟一次，飞行机组协助广播，并记录延误原因和广播时间

2 小时以上但在 3 小时以内乘务组为旅客发放餐饮,当乘务长在接到延误信息以后，应该及时致电 AOC 客户协调席

3 小时（含）以上且无明确起飞时间乘务组应及时向旅客进行广播，并记录延误原因和广播时间，且在不违反航空安全，安全保卫规定的情况下，安排旅客下飞机等待

航班延误地面等待期间，必须做好前后舱及出口的监控，如需发放餐食，则前后舱均需留人值守，防止不安全事件发生