Man has been storing up useful knowledge about himself and the universe at the rate which

has been spiraling upward for 10,000 years.

The【C1】______took a sharp upward leap with the invention of writing, but even【C2】______it remained painfully slow for several centuries. The next great leap forward【C3】______knowledge acquisition did not occur【C4】______the invention of movable type in the 15th century by Gutenberg and others.【C5】______to 1500, by the most optimistic【C6】______Europe was producing books at a rate of 1000 titles per year. This means that it【C7】______a full century to produce a library of 100,000 titles. By 1950, four and a half【C8】______later, the rate had accelerated so sharply that Europe was producing 120,000 titles a year.【C9】______once took a century now took only ten months. By 1960, a【C10】______decade later, the rate had made another significant jump,【C11】______a century's work could be finished in seven and a half months.【C12】______, by the midsixties, the output of books on a world【C13】______, Europe included, approached the prodigious(巨大的)figure of 900 titles per day.

One can【C14】______argue that every book is a net gain for the advancement of knowledge. Nevertheless we find that the accelerative【C15】______in book publication does, in fact, crudely【C16】______the rate at which man discovered new knowledge. For example, prior to Gutenberg【C17】______11 chemical elements were known. Antimony(锑)the 12th, was discovered【C18】______about the time he was working on his invention. It was fully 200 years since the 11th, arsenic(砒霜), had been discovered.【C19】______the same rate of discovery continued, we would by now have added only two or throe additional elements to the periodic table since Gutenberg.【C20】______, in the 450 years after his time, certain people discovered some seventy additional elements. And since 1900 we have been isolating the remaining elements not at a rate of one every two centuries, but of one every three years.

【C1】

A．knowledge

B．rate

C．development

D．accumulation