题目内容：

    Directions: For each blank in the following passage there are four words or phrases marked A, B, C and D. Fill in each blank with the word of phrase that best fits the context.

From the nation's earliest days, farming has held a crucial place in the American economy and culture. Farmers play an important role in any society, of course, since they feed people. But farming has been particularly ______ in the United States with intensified attention from civilians and government as well.

Early in the nation's life, farmers were seen as exemplifying economic ______ such as hard work, perseverance, and self-sufficiency. Moreover, many Americans, particularly immigrants who may have never held any land in the country, found that owning a farm was the ______ to enter the American economic system. They were immediately playing a part in the country’s economy.

The American farmer has generally been quite successful at producing food. Indeed, sometimes his success has created his biggest problem: the agricultural sector has suffered periodic explosions of overproduction that have ______ prices. When the government have to step in and ______ the worst of these events.

American farmers owe their ability to produce large yields to a number of factors. For one thing, they work under  ______ natural conditions. The American Midwest has some of the richest soil in the world. Rainfall is ______ over most areas of the country; rivers and underground water permit extensive irrigation where it is not.

Increasing use of high-quality  ______  labor also have contributed to the success of American agriculture. It is not unusual to see today's farmers  ______ plows or harvesters. One farmer can manage large lands of farms. Fertilizers and pesticides are commonly used although some environmentalists  ______ it. Computers track farm operations, and even  ______ technology is utilized to find the best places to plant and fertilize crops. US agriculture is among the most advanced in the world.

Farmers still fight with forces beyond their control, ______. Despite its generally benign weather, North America also experiences frequent floods and droughts. Changes in the weather give agriculture its own economic cycles, often  ______ the general economy. When negative factors hit farmers, calls for government assistance are particularly intense. In the 1930s, for instance, bad weather, and the Great Depression combined topush farms over the edge into a(n) ______ situation. The government responded with ______ agricultural reforms -- most notably, a system of price supports, whose significance toward the large-scale campaign lasted for many years.

1.A. valued B. accessed C. implemented D. illustrated

2.A. regulations B. virtues C. obligations D. requirements

3.A. shortcut B. implication C. reward D. substitute

4.A. maintained B. margined C. depressed D. refunded

5.A. take over B. cover up for C. come up with D. smooth out

6.A. varied B. favorable C. extreme D. visible

7.A. moderate B. predictable C. timely D. acid

8.A. labor B. investment C. chemical D. landscape

9.A. complicated B. flexible C. accessible D. executive

10.A. criticize B. recall C. evaluate D. identify

11.A. medical B. mobile C. space D. process

12.A. for example B. in all C. however D. additionally

13.A. subject to B. unrelated to C. reduced to D. applied to

14.A. vague B. desperate C. isolated D. feasible

15.A. struggling B. traditional C. sweeping D. permanent