[单项选择]Australia provides the only separate, ______ laboratory in which dramatic Quaternary extinction occurred.
A. natural continent-sized
B. natural and continent-sized
C. continent-sized natural
D. continent-sized and large

[单项选择]Australia provides the only separate, ______ laboratory in which dramatic Quaternary extinction occurred.
A. natural continent-sized
B. natural and continent-sized
C. continent-sized natural
D. continent-sized and large

[单项选择]In Australia, the Constitution can be changed only by ______.
A. referendum
B. British Queen
C. the Prime Minister
D. the Supreme Court

[单项选择]Only recently ______ possible to separate the components of fragrant substances and to determine their chemical composition.
A. it becomes
B. having become
C. has it become
D. which becomes

[单项选择]How does labor usually behave
A. labor would stipulate for money-wages.
B. labor would violently resist a reduction of real wages.
C. labor would strenuously resist a reduction of both money-wages and real wages.
D. labor would stipulate for real wages.

[单项选择]

Improvements in labor productivity 56 increase wages and salaries. Wages and salaries 57 about 75 percent of all income in the United States. 58 , labor productivity is the major 59 of this (and all other) nations’ living standards. If labor productivity improves because of an advance in technology, the 60 of output increases 61 the need for additional labor. The dollar value of all goods increases 62 , which implies that consumers ultimately receive more income.
Entrepreneurs have a profit 63 to increase labor productivity. They do so by providing their workers with better equipment and creating more efficient ways for their workers to use that equipment. Entrepreneurs also have an incentive to discover new products that are more highly valued 64 to their cost of production.
Some of the largest increases in productivity occur 65 major technological advancements. The steam
A. unavoidably
B. highly
C. ultimately
D. actually