F4 econ change in demand HELP!

1.In which of the following pairs does the demand for the first good creates a derived demand[1] for the second?
A.DVD and LD (laser disc) player --LD player播不到DVD的···
B.wool and mutton --羊毛多了人需要不代表羊肉也多了人需要
C.hardback book and printing paper -- 書是紙做的，當書需求上升時，自然也要用多了紙來做書
D.electricity and light bulb --開燈必然消耗電力，這是joint demand

2.Which of the following is an example of joint demand[2]?
A.the courier service of a local firm and the postal service of the government -- 用政府的postal service時誰說一定要同時用 某一間指定的公司的courier service？
B.the Airport Express train service and the Tung Chung Line train service --搭機場快線不一定要經用東涌線的
C.magazines and printing paper --要買printing paper才能看雜誌嗎？
D.floppy diskettes and floppy diskette drives --沒了drive，diskettes就不能用了

3. Which of the following is not implied by the law of demand[3]?
A. Relatively more high quality vergetables are sold in urban market than in rural market which are closer to the farms.--Alchian Generalization
B. An ad valorem tax on whisky leads to a greater drop in the sale of lower-priced whisky.--從價稅->價格%升幅一樣，但Sales下降了
C. People tend to eat more in buffet dinners than in ordinary dinners.--吃多了代表平均價格低了(Price跌)，吃多了代表Quantity Demand上升
D. The number of car accidents rises when the law reqires the drivers to wear seat belt.--Wear seat belt 令危險駕駛安全了(Cost下降)，所以多了人危險駕駛


[1] 引申需求：即是對一樣東西需求上升時，另一樣東西需求會同時上升
[2] 聯合需求：即是兩樣東西是互相依賴的（通常是一定要一起用）
[3] 需求定律：指Price(價格)和Qd(需求量)有相反關係(例如Price升時Od就會跌)，保持其他東西不變

2013-01-06 15:49:39 補充：
Quantity Demand -> Quantity Demanded (打錯字)