[常犯錯誤] 需求量Qd改變 vs 需求D改變

以下3題MC，共通點是? 同學一起找共通之處吧。

HKCEE 02/2/7
Which of the following would lead to the leftward shift of demand for Cross Harbour Bus Services from D1 to D2?
A. an increase in the toll fee for taxis using the cross harbour tunnels
B. an increase in the frequency of cross harbour bus services
C. a fall in the wage rate of bus drivers
D. a fall in the ticket price for Mass Transit Railway services

DSE pp/1/25
Which of the following can explain a leftward shift of the money demand curve?
A. a rise in the interest rate
B. an increase in income of households
C. a more widespread use of Octopus cards
D. an increase in the required reserve ratio

DSE 13/1/23
The aggregate demand curve will shift to the right if
A. there is a fall in the price level.
B. there is an improvement in technology.
C. the government reduces the import tariff.
D. the government reduces the salaries tax rate.

以上題目分別代表普通貨品或服務市場(需求D與供應S)、貨幣市場(貨幣需求Md與貨幣供應Ms)、總體經濟(總需求AD與總供應AS)。

而上述題目全部都是需求曲線、貨幣需求曲線或總需求曲線移動的情況，即所謂的需求改變，而原因是基於其他因素改變，即不是因為y軸(y-axis)variable (價格P, 名義利率R, 一般物價Price Level)改變而影響D, Md, AD。

選項A就往往就以不同的包裝，考大家相同的概念，亦是官方指定錯的「選項」。所有以上的選項A都代表了y-axis因素的改變，即需求量改變的概念，在圖顯示的話，應該要是沿曲線移動(D, Md, AD不會整條曲線左右移)。

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