硅在无机非金属材料中一直扮演着重要角色，被誉为无机非金属材料的主角。下列物品用到

根据老年人的生理和营养需求特点，膳食指南应增加哪一项（）

A.增加体力活动

B.增加餐次

C.食物烹调应清淡

D.增添绿叶蔬菜

E.食物要粗细搭配

小亮2小时走了8千米。他所走的路程和时间的比是（    ）。

（1）如图所示的装置中，重物M为重100N、边长10cm 的正方体，G重25N，重物G 恰好沿竖直方向匀速下降，若不计滑轮重及摩擦，那么物体M对水平桌面的压强为______Pa，所受桌面的摩擦力为______N．

（2）如图所示，长1m 重1.5N的均匀木板放在水平桌面上，木板左端离桌沿4dm 上面挂一诱饵．若一重0.5N 的老鼠偷吃食物，沿木板向左端爬去，根据杠杆的平衡条件______得出，当老鼠爬过离桌沿______dm 时，木板会失去平衡，而使它落入桌子下面的水桶中．

阅读理解。

     General Airport Tips

     Plan to get to the airport at least an hour early, or two during holidays and other busy times; this will

reduce the stress of the flight. If all goes well, you will have time to relax, shop for last-minute items, or

have a meal before the flight.

      Flight Delays

     Find out why your flight is delayed. Call the free call numbers. Find out if other airlines are experiencing

similar delays. If you believe the delay is due to something other than weather or air traffic problems, then

mention your suspicion (怀疑) and ask the airline agent to book you on the next available flight, either on the

same air-line or a competing one. This is called "Rule 240", and all airlines are required to do it. Use the lingo

(行话); ask,"Can you 240 me?" when speaking with an agent. They will know what you mean.

     Flight Cancellations (取消)

     If your flight is canceled, then make a reservation on the next flight to your destination. Usually, air-line

personnel will try to book everyone on their next flight out. Often they will put you on a competitor's next

flight only if you request it. If on-time arrival is important to you, when you check flights through our

reservation system you can rate your choices based on their on-time arrival records. Be sure to also check the

weather conditions, as they often affect flight schedules.

1. A person goes to the airport ahead of time mainly to _______.

A. buy what he wants in the airport

B. have a good rest in the airplane

C. reduce the pressure of the flight

D. get on the airplane immediately

2. If a person calls "Rule 240", he wants to _______.

A. change for the ticket to the next flight

B. make sure the time for the next plane

C. know if other flights' delays happen

D. ask the reason for the plane delay

3. After a flight cancellation, a passenger can_______.

A. arrive at his destination on time

B. be arranged on a competing flight

C. make sure the weather is quite fine

D. reserve the next flight to your destination

4. The purpose in writing this text is to________.

A. show us how to get on a plane

B. tell us what to do before and after a flight

C. put forward suggestions for a flight

D. teach us actions before an emergency

分支语句分为条件语句和 【7】 。