下列叙述中，因我国人口数量过多而带来的负面影响是[ ] A．劳动力短缺 B．兵源
题型：选择题
问题：
下列叙述中，因我国人口数量过多而带来的负面影响是[ ]
A．劳动力短缺
B．兵源不足
C．人口老龄化严重
D．住房紧张，就业困难
题型：选择题
Do you know anything about airport security(安全)? In order to protect passengers, airports have 小题1:________rules. Some of these rules include:
Restricted items
小题2:________ are not allowed on board. In the past, knives under four inches were allowed on board, 小题3:________ now, knives are not permitted at all.
ID checks
All passengers must have ID cards 小题4:________ match their boarding passes. Passengers are unable to fly小题5:_________these documents.
Security on the aircraft
Generally, 小题6:________ are not permitted to enter the cockpit, where the pilot sits, 小题7:________when the plane is in the air. In order to increase security, bullet-proof doors and locks are now standard on all planes.
Forbidden liquids
No liquids over 100ml may be 小题8:________ on board in hand luggage. Liquids 小题9:______ 100ml must be carried in a clear plastic bag. This 小题10:________water, shampoo, toner etc