Welfare economics is the study of（）
A. taxes and subsidies
B. how technology is best put to use in the production of goods and services
C. government welfare programs for needy people
D. how the allocation of resources affects economic well-being
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Suppose Iran imposes a tariff on lumber. For the tariff to have any effect, it must be the case that（）
A. Iran is an exporter of lumber
B. the domestic quantity of lumber supplied exceeds the domestic quantity of lumber demanded at the world price without the tariff
C. the world price without the tariff is less than the price of lumber without trade
D. the world price without the tariff is greater than the price of lumber without trade
Which of the underlined What- structures functions differently from the others（）
A. What gave it an air of intensity was that Daisy lived there
B. I have been impressed by what he presented
C. Would you please translate into Chinese what’s written on the blackboard
D. What do you know about the coming contest
The terminal voltage of all parallel components is of（）
A. the same voltage
B. the different voltage
C. the same current
D. the different current
Please choose the best answer for each incomplete sentence. The early achievements in space exploration were all crash-landings, each spacecraft___（）
A. having been destroying
B. in destroy
C. destroying
D. being destroyed
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