【单选题】

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 engine and the internal combustion engine are two examples. The advances in the computer industry have been 66 phenomenal.Advances in technology depend 67 on businesses making 68 investment in new technology and new products.A、major issue in today’s economy is 69 businesses are doing this and what incentives are being provided by the government to companies to encourage investment.Another issue is whether labor productivity in the United States has 70 other countries.
There have also been 71 increases in productivity in our agricultural 72 .Because of the increased use of chemicals, the 73 per acre are many times greater than they were 100 years ago, and consequently, 74 Americans now 75 farming, yet agricultural output is the highest it has, ever been.
A、rateB、ratioC、velocity
D、ration