Many college students today own personal computers that cost anywhere from $ 1 000 to perhaps $5 000 or more.【B1】______, it is not uncommon for them to purchase【B2】_______ costing another several hundred dollars. Twenty years ago, computers were【B3】______, but they were very large and extremely expensive. Few, if any,【B4】______purchased computers for home use. Over the years, the price of the 'guts' Of a computer its memory—has declined to less than a thousandth of the price per unit of memory that prevailed twenty years ago. This is the main reason why computers cost so much less today than they used to. Moreover,【B5】______improvements have made it possible to【B6】______memory circuitry that is small enough to fit into the portable personal computers that many of us own and use.【B7】______, as the price of computation has declined the average consumer and business have spent more on purchasing computers. 【B8】______, improved agricultural technology, hybrid(杂交)seeds,【B9】______animal breeding, and so on have vastly increased the amount of output a typical farmer can produce. The prices of goods such as meats and grains have fallen sharply relative to the prices of most other goods and services. As agricultural prices have fallen, many households have decreased their total expenses on food. Even though the【B10】______of a product purchased generally increases when its price falls, total expenses on it may decline. 【B1】